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Home My WebLink AboutEX10_RS_DrainageTIR_CamelliaCourt_230802_v22023 D. R. STRONG Consulting Engineers Inc. Camellia Court Technical Information Report Renton, Washington TECHNICAL INFORMATION REPORT for CAMELLIA COURT 99, 101 & 107 WILLIAMS AVE S RENTON, WASHINGTON 98057 ____________________________________________________________________________ DRS Project No. 23003 Renton File No. PRE22-000078 Owner/Applicant Leon Cohen General Consulting Services 9219 SE 33rd PL Mercer Island, WA 98040 Report Prepared by D. R. STRONG Consulting Engineers 620 7th Avenue Kirkland, WA 98033 (425) 827-3063 Report Issue Date August 2, 2023 EXHIBIT 10 RECEIVED PLANNING DIVISION 11/01/2023 AVanGordon DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 2023 D. R. STRONG Consulting Engineers Inc. Camellia Court Technical Information Report Renton, Washington TECHNICAL INFORMATION REPORT CAMELLIA COURT TABLE OF CONTENTS SECTION I ...................................................................................................................... 4 Project Overview ......................................................................................................... 4 Predeveloped Site Conditions ..................................................................................... 4 Developed Site Conditions .......................................................................................... 4 King County Area, Washington .................................................................................. 13 Ur-urban land ......................................................................................................... 13 SECTION II ................................................................................................................... 14 Conditions and Requirements Summary ................................................................... 14 Conditions of Approval............................................................................................... 17 SECTION III .................................................................................................................. 18 Off-Site Analysis ........................................................................................................ 18 Task 1: Define and Map Study Area ...................................................................... 18 Task 2: Resource Review ...................................................................................... 19 Task 3: Field Inspection ......................................................................................... 28 Task 4: Drainage System Description and Problem Descriptions .......................... 29 Task 5: Mitigation of Existing or Potential Problems .............................................. 31 SECTION IV .................................................................................................................. 37 Flow Control Analysis and Water Quality Design ...................................................... 37 Existing Site Hydrology .......................................................................................... 37 Developed Site Hydrology ...................................................................................... 39 SECTION V ................................................................................................................... 41 Conveyance System Analysis and Design ................................................................ 41 SECTION VI .................................................................................................................. 42 Special Reports and Studies ..................................................................................... 42 SECTION VII ................................................................................................................. 43 Other Permits, Variances and Adjustments ............................................................... 43 SECTION VIII ................................................................................................................ 44 CSWPPP Analysis and Design (Part A) .................................................................... 44 SWPPP Plan Design (Part B) .................................................................................... 44 SECTION IX .................................................................................................................. 46 Bond Quantities, Facility Summaries, and Declaration of Covenant .......................... 46 SECTION X ................................................................................................................... 47 Operations and Maintenance Manual ........................................................................ 47 DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 2023 D. R. STRONG Consulting Engineers Inc. Camellia Court Technical Information Report Renton, Washington APPENDICES ............................................................................................................... 48 Appendix “A” Legal Description ................................................................................. 49 Appendix “B” WWHM Modeling Results .................................................................... 50 Appendix “C” Bond Quantity Worksheet .................................................................... 51 List of Figures Figure 1 TIR Worksheet .................................................................................................. 5 Figure 2 Vicinity Map ..................................................................................................... 10 Figure 3 Drainage Basins, Subbasins, and Site Characteristics ................................... 11 Figure 4 Soils ................................................................................................................ 12 Figure 5 City of Renton Topography Map ..................................................................... 20 Figure 6 City of Renton erosion Hazard Areas Map ...................................................... 21 Figure 7 City of Renton Flood Hazards Map ................................................................. 22 Figure 8 City of Renton Streams & Wetlands Map ........................................................ 23 Figure 9 City of Renton Landslide Hazards Map ........................................................... 24 Figure 10 City of Renton Seismic Hazard Areas Map ................................................... 25 Figure 11 FEMA Map .................................................................................................... 26 Figure 12 City of Renton Drainage Complaints Map ..................................................... 27 Figure 13 Offsite Analysis Downstream Map ................................................................ 32 Figure 14 Offsite Analysis Downstream Table .............................................................. 33 Figure 15 Predeveloped Area Map................................................................................ 38 Figure 16 Developed Area Map .................................................................................... 40 DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 2023 D. R. STRONG Consulting Engineers Inc. Page 4 Camellia Court Technical Information Report Renton, Washington SECTION I PROJECT OVERVIEW The Project is the proposed development of three parcels with a 6-story, 95 unit residential building. The Project is located at 99, 101 & 107 Williams Ave S, Renton, Washington (Site) also known as Tax Parcel Numbers 0007200-0096, 723150-2130, and 723150-2125. The Project will meet the drainage requirements of the 2022 City of Renton Surface Water Design Manual (Manual) PREDEVELOPED SITE CONDITIONS The total existing Site area is approximately 17,262 s.f. (0.396 acres). The total Project area is 19,262 s.f. (0.439 acres), which includes the Site, the sidewalk area within Williams Avenue S ROW to be reconstructed and the proposed paving within the alley. The Site is currently developed with a single family home, a duplex, a multi-unit commercial building, concrete and gravel parking area, and landscaping. The Site is generally flat with a shallow grade to the west and is contained within one Threshold Discharge Area (TDA). Runoff from the Site generally leaves via sheet flow in one of three directions. Due to the flat slopes it is difficult to establish the exact extents of the areas which drain to the three natural discharge locations. The first natural discharge location is the western property line along the alley. Runoff here is collected by the storm drain system in the alley and conveyed north. The second natural discharge location is along the south property line along the alley Runnoff here is collected by catch basins and conveyed east towards the storm main in Williams Ave S via pipe. The third natural discharge location is along the eastern project with runoff draining to the curb along Williams Ave S. This includes roof runoff from the southernmost building which discharges via pipe to the gutter. Gutter flow generally travels north to an existing offsite catch basin. Runoff from all NDAs converges within the ¼ mile and therefore the Site will be considered to be one TDA. Drainage basins and natural discharge locations for the Site are shown in Figure 3. The existing Site coverage is shown in Figure 15 DEVELOPED SITE CONDITIONS The applicant is seeking approval to develop three parcels totalling 0.396 acres into a 6- story, 95-unit residential building (Project). All existing improvements located on the Site will be demolished or removed during construction. The project is required to meet the City’s Peak Rate Flow Control Standard (Existing Conditions) and Enhanced Basic Water Quality treatment. This standard matches the developed Site peak flow rates to the peak flow rates of existing conditions. The proposed impervious surface areas are as follows: roof area of the proposed building, sidewalk, curb and gutter along Williams Ave S and paving along alley. The Project will generate approximately 18,976 s.f. of impervious area (0.436 acres). Total new and replaced pollution generating surfaces (PGIS) will be below the 5,000 s.f. threshold for requiring water quality treatment. The Project will result in less than a 0.15 CFS increase in the 100-year peak flow rate when compared to the existing conditions, so no flow control facility will be required. Proposed Site cover and surfaces are show in Figure 16, Developed Site Conditions. (See Section IV). DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 2023 D. R. STRONG Consulting Engineers Inc. Page 5 Camellia Court Technical Information Report Renton, Washington FIGURE 1 TIR WORKSHEET TECHNICAL INFORMATION REPORT (TIR) WORKSHEET Part 1 PROJECT OWNER AND PROJECT ENGINEER Part 2 PROJECT LOCATION AND DESCRIPTION Project Owner: Leon Cohen Phone: (206) 714-8237 Address: 9219 SE 33rd PL Mercer Island, WA 98040 Project Engineer: Jonathan S. Murray, P.E. Company: D. R. STRONG Consulting Engineers Phone: (425) 827-3063 Project Name: Camellia Court DDES Permit#: PSUB23-000123 Location: Township: 23 North Range: 05 East Section: 17 Site Address: 99, 101, 107 Williams Ave S, Renton, WA 98057 Part 3 TYPE OF PERMIT APPLICATION Part 4 OTHER REVIEWS AND PERMITS Land use Services (Subdivision/ Short Subd. /UPD) Building Services (M/F / Commercial / SFR) Clearing and Grading Right-of-Way Other: ________________________ DFW HPA Shoreline Management COE CWA 404 Structural Rockery/Vault/_____ ECY Dam Safety DOE Dam Safety ESA Section 7 FEMA Floodplain COE Wetlands Other: ________________________ Part 5 PLAN AND REPORT INFORMATION Technical Information Report Type of Drainage Review (Full) / Targeted / Simplified/ Large Site/ Directed (circle): Date (include revision __________________ Dates): __________________ Date of Final: _______________________ Site Improvement Plan (Engr. Plans) Type (circle one): (Full) / Modified / Simplified Date ( include revision _____________ Dates): _____________ Date of Final _____________ DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 2023 D. R. STRONG Consulting Engineers Inc. Page 6 Camellia Court Technical Information Report Renton, Washington Part 6 ADJUSTMENT APPROVALS Type (circle one): Standard / Experimental / Blanket Description: (include conditions in TIR Section 2) _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________ Approved Adjustment No. ______________________ Date of Approval:_______________________ Part 7 MONITORING REQUIREMENTS Monitoring Required: (Yes)/ No Start Date: ______TBD________ Completion Date __________________ Describe: __________________________ ___________________________________ ___________________________________ Re: KCSWDM Adjustment No.____________ Part 8 SITE COMMUNITY AND DRAINAGE BASIN Community Plan: _________________________________ Special District Overlays:_N/A________________________________ Drainage Basin:_ Lower Cedar River/Cedar Main Urban Sub Basin_______ Stormwater Requirements: Peak Rate Flow Control Standard (Matching Existing Conditions) and Enhanced Basic WQ Treatment Part 9 ONSITE AND ADJACENT SENSITIVE AREAS River/ Stream_______________________ Lake ______________________________ Wetlands___________________________ Closed Depression___________________ Floodplain__________________________ Other Aquifer Protection Area (Zone 1) Steep Slope____________________ Erosion Hazard__________________ Landslide Hazard________________ Coal Mine Hazard________________ Seismic Hazard__________________ Habitat Protection________________ ________________________________ DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 2023 D. R. STRONG Consulting Engineers Inc. Page 7 Camellia Court Technical Information Report Renton, Washington Part 10 SOILS Soil Type _______Ur________ _________________ _________________ Slopes ______8-15%______ _________________ _________________ Erosion Potential _Moderate to Severe _________________ _________________ High Groundwater Table (within 5 feet) Sole Source Aquifer other __________________________ Seeps/Springs Additional Sheets Attached Part 11 DRAINAGE DESIGN LIMITATIONS REFERENCE Core Requirement #2 –Offsite Analysis Sensitive / Critical Areas SEPA Aquifer Protection Area Additional Sheet Attached LIMITATION / SITE CONSTRAINT ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ Part 12 TIR SUMMARY SHEET (provide one TIR Summary Sheet per Threshold Discharge Area) Threshold Discharge Area: Site comprised of one TDA (name or description) Core Requirements (all 8 apply) Discharge of Natural Location Number of Natural Discharge Locations: 2 Offsite Analysis Level: 1 / 2 / 3 dated:________________ Flow Control Level: 1 / 2 / 3 or Exemption Number_________ (incl. facility summary sheet Flow Control BMPs___________________________ Conveyance System Spill containment located at: TBD__________________ Erosion and Sediment Control/ ESC Site Supervisor:_ TBD____________________ Construction Stormwater Contact Phone:______TBD____________________ Pollution Prevention After Hours Phone:_TBD_____________________ Maintenance and Operation Responsibility: Private / Public If Private, Maintenance Log Required: Yes / No Financial Guarantees and Provided: Yes / No Liability Water Quality Type: Basic / Sens. Lake / Enhanced Basic / Bog (include facility summary sheet) or exemption No. _____________________ Landscape Management Plan: Yes / No DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 2023 D. R. STRONG Consulting Engineers Inc. Page 8 Camellia Court Technical Information Report Renton, Washington Special Requirements (as applicable) Area Specific Drainage Type: CDA / SDO / MDP / BP / LMP / Shared Fac. / None Requirements Name:_____________________________________ Floodplain/Floodway Delineation Type: Major / Minor / Exemption / None 100-year Base Flood Elevation (or range):_______ Datum: Flood Protection Facilities Describe: N/A Source Control Describe Landuse: M/F Residential (comm. / industrial landuse) Describe any structural controls: N/A Oil Control High-use Site: Yes / No Treatment BMP: ________________________ Maintenance Agreement: Yes / No with whom?_______________________________ Other Drainage Structures Describe: Part 13 EROSION AND SEDIMENT CONTROL REQUIREMENTS MINIMUM ESC REQUIREMENTS DURING CONSTRUCTION Clearing Limits Cover Measures Perimeter Protection Traffic Area Stabilization Sediment Retention Surface Water Collection Dewatering Control Dust control Flow Control Protection of Flow Control BMP Facilities (existing and proposed) Maintain BMPs/ Manage Project MINIMUM ESC REQUIREMENTS AFTER CONSTRUCTION Stabilize Exposed Surfaces Remove and Restore Temporary ESC Facilities Clean and Remove All Silt and Debris, Ensure Operations of Permanent Facilities, restore operation of Flow Control BMP Facilities as necessary Flag limits of SAO and open space preservation areas Other __________________________ DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 2023 D. R. STRONG Consulting Engineers Inc. Page 9 Camellia Court Technical Information Report Renton, Washington Part 14 STORMWATER FACILITY DESCRIPTIONS (Note: Include Facility Summary and Sketch Flow Control Description Water Quality Description On-Site BMPs Description Detention Infiltration Regional Facility Shared Facility Other _________ _________ _________ _________ _________ Vegetated Flowpath Wetpool Filtration Oil Control Spill Control Other _________ _________ _________ _________ _________ _________ Full Dispersion Full Infiltration Limited Infiltration Rain Garden Bioretention Permeable Pavements Basic Dispersion Soil Amendment Perforated Pipe Connection Other _________ _________ _________ _________ _________ _________ _________ _________ _________ _________ Part 15 EASEMENTS/TRACTS Part 16 STRUCTURAL ANALYSIS Drainage Easement Covenant Native Growth Protection Covenant Tract Other: Cast in Place Vault Retaining Wall Rockery > 4’ High Structural on Steep Slope Other: Part 17 SIGNATURE OF PROFESSIONAL ENGINEER I or a civil engineer under my supervision have visited the site. Actual site conditions as observed were incorporated into this worksheet and the attachments. To the best of my knowledge the information provided here is accurate. Signed/Date DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 2023 D. R. STRONG Consulting Engineers Inc. Page 10 Camellia Court Technical Information Report Renton, Washington FIGURE 2 VICINITY MAP Site DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 2023 D. R. STRONG Consulting Engineers Inc. Page 11 Camellia Court Technical Information Report Renton, Washington FIGURE 3 DRAINAGE BASINS, SUBBASINS, AND SITE CHARACTERISTICS DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 0 GRAPHIC SCALE 15 30 45 1 INCH = 30 FT. DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 2023 D. R. STRONG Consulting Engineers Inc. Page 12 Camellia Court Technical Information Report Renton, Washington FIGURE 4 SOILS DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 2023 D. R. STRONG Consulting Engineers Inc. Page 13 Camellia Court Technical Information Report Renton, Washington KING COUNTY AREA, WASHINGTON UR-URBAN LAND Map Unit Setting • Urban land: 100 percent • Estimates are based on observations, descriptions, and transects of the mapunit. Description of Urban Land Interpretive groups • Land capability classification (irrigated): None specified • Land capability classification (nonirrigated): 8 • Hydric soil rating: No DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 2023 D. R. STRONG Consulting Engineers Inc. Page 14 Camellia Court Technical Information Report Renton, Washington SECTION II CONDITIONS AND REQUIREMENTS SUMMARY The Project must comply with the following Core and Special Requirements: • C.R. #1 – Discharge at the Natural Location: Existing drainage discharges from Site at three locations but converges within ¼ mile from the Site, indicating it’s contained within one TDA. Developed discharge from the project will be directed south to an existing catch basin within the alley. • C.R. #2 – Offsite Analysis: Analysis is included in Section III. The Analysis describes the Site’s runoff patterns in detail. • C.R. #3 – Flow Control: The Project is required to meet the City’s Peak Rate Flow Control Standard (Existing Conditions). The Site is required to “match the developed peak discharge rates to existing site conditions peak discharge rates for 2-, 10-, and 100-year return periods,” (2022 City of Renton Surface Water Design Manual, Sec. 1.2.3.1). The Project will result in less than an 0.15 CFS increase in the 100-year peak flow and therefore qualifies for an exception from providing a flow control facility. • C.R. #4 – Conveyance System: New pipe systems are required to be designed with sufficient capacity to convey and contain (at minimum) the 25-year peak flow, assuming developed conditions for onsite tributary areas and existing conditions for any offsite tributary areas. Pipe system structures may overtop for runoff events that exceed the 25-year design capacity, provided the overflow from a 100-year runoff event does not create or aggravate a “severe flooding problem” or “severe erosion problem” as defined in C.R. #2. Any overflow occurring onsite for runoff events up to and including the 100-year event must discharge at the natural location for the project site. In residential subdivisions, such overflow must be contained within an onsite drainage easement, tract, covenant or public right-of-way. This analysis will be provided during final engineering. • C.R. #5 – Erosion and Sediment Control: The Project will provide the seven minimum ESC measures. A temporary erosion and sedimentation control plan will be provided as part of the engineering construction plan set. • C.R. #6 – Maintenance and Operations: Maintenance of the proposed storm drainage facilities will be the responsibility of the City. An Operation and Maintenance Manual will be provided during final engineering. • C.R. #7 – Financial Guarantees: Prior to commencing construction, the Applicant must post a drainage facilities restoration and site stabilization financial guarantee. For any constructed or modified drainage facilities to be maintained and operated by the City, the Applicant must: 1) Post a drainage defect and maintenance financial guarantee for a period of two years, and 2) Maintain the drainage facilities during the two-year period following posting of the drainage defect and maintenance financial guarantee. DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 2023 D. R. STRONG Consulting Engineers Inc. Page 15 Camellia Court Technical Information Report Renton, Washington • C.R. #8 – Water Quality: The Project is exempt from providing water quality treatment due to creating less than 5,000 s.f. of new plus replaced pollution generating surfaces. • C.R. #9 – On-Site BMPs: The Project is required to provide on-site BMPs to mitigate the impacts of storm and surface water runoff. Small lot BMPs were determined by the BMP requirements outlined in Section 1.2.9.2.1 of the CORSWDM. As required by the CORSWDM, small lot BMP requirements were analyzed in the order of preference listed in section 1.2.9.2.1. 1. Full Dispersion: There is an insufficient amount of native growth in order to utilize full dispersion. The lack of required undisturbed area and flowpath lengths means that full dispersion is infeasible for this Project. 2. Full Infiltration: Infiltration based BMPS are prohibited within Zone 1 of the Aquifer Protection Area. 3. All target surfaces not mitigated by requirements 1 and 2 above must be mitigation to the maximum extent feasible using one or more of the following BMPs • Limited Infiltration: Infiltration based BMPS are prohibited within Zone 1 of the Aquifer Protection Area. • Rain Gardens: Infiltration based BMPS are prohibited within Zone 1 of the Aquifer Protection Area. • Bioretention: Infiltration based BMPS are prohibited within Zone 1 of the Aquifer Protection Area. • Permeable Pavement: Infiltration based BMPS are prohibited within Zone 1 of the Aquifer Protection Area. 4. Basic Dispersion: Due to the site layout and coverage for this Project, there is no area available for a flowpath that will meet the requirements of the manual for basic dispersion. BMPS must be implemented at a minimum of 20% for lots between 11,000 and 22,000 square feet. For Projects located in Zone 1 of the Aquifer Protection Area these impervious area amounts must be doubled. For this Project the requirement would be 6,575 s.f. Since the BMPS from requirements 1, 2, 3 and 4 above are not feasible the project will implement one or more of the following BMPs to the maximum extent feasible. • Reduced Impervious Surface Credit: Each of the various methods of reduced impervious surface credit are not feasible for this Project. Restricted footprint is not feasible as the proposed building footprint will exceed 4,000 s.f., Wheel strip driveway is not feasible as the project proposes no surface level driveways. Minimum disturbance foundations are not applicable for the foundation requirements of the proposed building in addition to the need for underground parking. Open grid decking over pervious surfaces is not feasible because there are no proposed pervious surfaces. • Native Growth Retention Credit: There is no existing native vegetated surfaces on the Site. DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 2023 D. R. STRONG Consulting Engineers Inc. Page 16 Camellia Court Technical Information Report Renton, Washington • Tree Retention Credit: The Project is not proposing to retain any trees within the Site but will retain two trees along the project frontage. Per the CORSWDM, a perforated stub out connection is required for a project that proposes the connection of roof downspouts to the local drainage system. However, there is no available locations for a perforated stub out connection which will meet the setback requirements. • S.R. #1 – Other Adopted Area-Specific Requirements: Not applicable for this Project. • S.R. #2 – Flood Hazard Area Delineation: Not applicable for this Project. • S.R. #3 – Flood Protection Facilities: Not applicable for this Project. • S.R. #4 – Source Control: Not applicable for this Project. • S.R. #5 – Oil Control: Not applicable for this Project. • S.R. #6 – Aquifer Protection Area: Site is located within Aquifer Protection Zone 1. No infiltration is proposed as a part of this Project. DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 2023 D. R. STRONG Consulting Engineers Inc. Page 17 Camellia Court Technical Information Report Renton, Washington CONDITIONS OF APPROVAL TBD DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 2023 D. R. STRONG Consulting Engineers Inc. Page 18 Camellia Court Technical Information Report Renton, Washington SECTION III OFF-SITE ANALYSIS LEVEL ONE DOWNSTREAM ANALYSIS DISCLAIMER: This report was prepared at the request of Leon Cohen for the 0.396 acre parcels known as a portion of the Northwest Quarter of Section 17, Township 23 North, Range 5 East, W.M., in King County, Tax Parcel Numbers 0007200-0096, 723150-2130, and 723150-2125 (Site). D. R. STRONG Consulting Engineers Inc. (DRS) has prepared this report for the exclusive use of DRS, the owner, and their agents, for specific application to the development project as described herein. Use or reliance on this report, or any of its contents for any revisions of this project, or any other project, or by others not described above, is forbidden without the expressed permission by DRS. TASK 1: DEFINE AND MAP STUDY AREA This Offsite Analysis was prepared in accordance with Core Requirement #2, Section 1.2.2 of the 2022 City of Renton Surface Water Design Manual (Manual). The Site is located at 99, 101, & 107 Williams Ave S, Renton, Washington. The Project is the development of three parcel into a 6-story, 95-unit residential building. See Figures 2 through 13 for maps of the study area. DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 2023 D. R. STRONG Consulting Engineers Inc. Page 19 Camellia Court Technical Information Report Renton, Washington TASK 2: RESOURCE REVIEW • Adopted Basin Plans: King County Department of Permitting and Environmental Review (DPER) and Department of Natural Resources and Parks (DNRP) Lower Cedar River Basin Plan Summary • Finalized Drainage Studies: No available applicable drainage studies at this time. • Basin Reconnaissance Summary Reports: Cedar River Current and Future Conditions Report (April 1993). • Comprehensive Plans: Renton’s Comprehensive Plan, adopted on June 22, 2015, effective Ju ly 1, 2015. • Floodplain/Floodway (FEMA) Map: The Site is not located within the 100-year floodplain but is located within the 500-year “Other Flood Area, Zone X” area, See Figure 11. • Other Offsite Analysis Reports: N/A • Sensitive Areas Map Folios: See Figures 6-10. • DNRP Drainage Complaints and Studies: Per King County Water and Land Resources Division, there were no complaints within the downstream paths, within approximately one mile from the Site within the last 10 years. See Figure 12. • USDA King County Soils Survey: See Figure 4 • Wetlands Inventory: Vol. 2 East (1990) – No wetlands identified along the downstream paths in the KC Wetlands Inventory. The City of Renton Mapping Applications indicates there are also no wetlands along the downstream path. See Figure 8. • Migrating River Studies: The Site is not located near the channel migration zones of Cedar River, Tolt River, Raging River, Snoqualmie River, or Green River. • King County Designated Water Quality Problems: Per the Washington State Water Quality Assessment 303(d)/305(b) Integrated Report current as of 2012, the reach of the Cedar River will outlet to has three category 5 listings, one category 2 listing, and three category 5 listings. • King County Designated Water Quality Problems: Per the Washington State Water Quality Assessment 303(d)/305(b) Integrated Report current as of 2012, there are no water quality problems within 1 mile downstream of the Site. DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 2023 D. R. STRONG Consulting Engineers Inc. Page 20 Camellia Court Technical Information Report Renton, Washington FIGURE 5 CITY OF RENTON TOPOGRAPHY MAP Site DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 2023 D. R. STRONG Consulting Engineers Inc. Page 21 Camellia Court Technical Information Report Renton, Washington FIGURE 6 CITY OF RENTON EROSION HAZARD AREAS MAP Site DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 2023 D. R. STRONG Consulting Engineers Inc. Page 22 Camellia Court Technical Information Report Renton, Washington FIGURE 7 CITY OF RENTON FLOOD HAZARDS MAP Site DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 2023 D. R. STRONG Consulting Engineers Inc. Page 23 Camellia Court Technical Information Report Renton, Washington FIGURE 8 CITY OF RENTON STREAMS & WETLANDS MAP Site DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 2023 D. R. STRONG Consulting Engineers Inc. Page 24 Camellia Court Technical Information Report Renton, Washington FIGURE 9 CITY OF RENTON LANDSLIDE HAZARDS MAP Site DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 2023 D. R. STRONG Consulting Engineers Inc. Page 25 Camellia Court Technical Information Report Renton, Washington FIGURE 10 CITY OF RENTON SEISMIC HAZARD AREAS MAP Site DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 2023 D. R. STRONG Consulting Engineers Inc. Page 26 Camellia Court Technical Information Report Renton, Washington FIGURE 11 FEMA MAP Site (Approximate) DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 2023 D. R. STRONG Consulting Engineers Inc. Page 27 Camellia Court Technical Information Report Renton, Washington FIGURE 12 CITY OF RENTON DRAINAGE COMPLAINTS MAP Site DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 2023 D. R. STRONG Consulting Engineers Inc. Page 28 Camellia Court Technical Information Report Renton, Washington TASK 3: FIELD INSPECTION UPSTREAM TRIBUTARY AREA Upon evaluation of the upstream area through examining COR topographic map (see Figure 5) and by conducting field reconnaissance on January 24, 2023, the upstream tributary area for the Site is considered negligible. The parcels to the north sheet flow to the conveyance system on the alley to the west and the parcel to the south appears to be directly piped to the conveyance system on the alley south of the site GENERAL ONSITE AND OFFSITE DRAINAGE DESCRIPTIONS The Site is contained within one Threshold Discharge Area (TDA). Runoff from the Site generally leaves via sheet flow in one of three directions. The first natural discharge location is the western property line along the alley. Runoff here is collected by the storm drain system in the alley and conveyed north. The second natural discharge location is along the south property line along the alley. Runoff here is collected by catch basins and conveyed east towards the storm main in Williams Ave S via pipe. The third natural discharge location is along the eastern project with runoff draining to the curb along Williams Ave S. This includes roof runoff from the southernmost building which discharges via pipe to the gutter. Gutter flow generally travels north to an existing offsite catch basin. Runoff from NDA 1, and NDAs 2 and 3 converges on S Tillicum St and Williams Ave S flowing in a northerly direction before reaching its outfall. A DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 2023 D. R. STRONG Consulting Engineers Inc. Page 29 Camellia Court Technical Information Report Renton, Washington TASK 4: DRAINAGE SYSTEM DESCRIPTION AND PROBLEM DESCRIPTIONS DRAINAGE SYSTEM DESCRIPTION The downstream analysis is further illustrated and detailed in the Downstream Map Figure 13 and Downstream Table Figure 14. The drainage area is located within the Lower Cedar River. The drainage area was evaluated by reviewing available resources described in Task 2, and by conducting a field reconnaissance on January 1, 2023 under overcast conditions. DOWNSTREAM PATH 1 “NDL 1” is the natural discharge location for NDA 1. It is located along the western property line of the northern portion of the Site. No concentrated flow was observed. Point “A1”, is a Type 1 catch basin collecting sheet flow runoff from NDA 1. From Point “A1” to Point “A2”, runoff is conveyed in a northerly direction as pipe flow via an 8” diameter PVC pipe (±0’-±222’) Point “A2”, is a Type 1 catch basin. (±222’) From Point “A2” to Point “A3”, runoff is conveyed in a northerly direction as pipe flow via an 8” PVC pipe. Moderate flow was observed (±222’-376’). Point “A3” is a Type 1 catch basin. (±376’) From Point “A3” to Point “A4”, runoff is conveyed westerly as pipe flow via 12” RCP. Did not observed (±376’-487’). Point “A4” is a Type 1 catch basin. (±487’) From Point “A4 to Point “A5” runoff is conveyed westerly as pipe flow via a 12” RCP. Did not observed. (±487-±516’) Point “A5” is a Type 2 catch basin manhole. (±516’) From Point “A5” to Point “A6”, runoff is conveyed northerly as pipe flow via a 8” RCP. Did not observed. (±587’-±609’) Point “A6” is a Type 2 catch basin manhole. (±609’) From Point “A6” to Point “A7”, runoff is conveyed in a northerly direction as pipe flow via 8” RCP. Did not observed. (±609’-±650’) Point “A7” is a Type 2 catch basin manhole. (±650’) From Point “A7” to Point “A8”, runoff is conveyed in an easterly direction as pipe flow via an 8” RCP. Did not observed. (±650’-±791’) Point “A8” is a Type 2 catch basin manhole. (±791’) From Point “A8” to Point “A9”, runoff is conveyed in a easterly direction as pipe flow via an 8” RCP. Did not observed (±791’-±929’). Point “A9” is a Type 2 catch basin manhole and the convergence point for the runoff from NDA 1 and NDA 2. DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 2023 D. R. STRONG Consulting Engineers Inc. Page 30 Camellia Court Technical Information Report Renton, Washington From Point “A9” to Point “A10”, runoff is conveyed in a northerly direction as pipe flow via a 12” RCP. Did not observed (±929’-±1,017’). Point “A10” is the outfall to Cedar River. Cedar River flows west. DOWNSTREAM PATH 2 “NDL 2” is the natural discharge location for NDA 2. It is located along the southern property line in the southern portion of the Site Point “B1” is a Type 1 catch basin. The collected roof runoff from the commercial building appears to be piped directly to this catch basin. From Point “B1” to Point “B2”, runoff continues in a westerly direction as pipe flow via an 8” DI pipe. No concentrated flow was observed (±0’-±67’) Point “B2” is a Type 1 catch basin. (±67’) From Point “B2” to Point “B3,” runoff continues in a westerly direction as pipe flow via an 8” DI pipe. (±67’-±118’) Point “B3” is a Type 1 catch basin. (±118’) From Point “B3” to Point “B4”, runoff continues in a northerly direction as pipe flow via an 8” RCP. Did not observed. (±118’-±176’) Point “B4” is a Type 2 catch basin manhole. (±176’) From Point “B4” to Point “B5”, runoff continues in a northerly direction as pipe flow via an 8” RCP. Did not observed. (±176’-±326’) Point “B5” is a Type 2 catch basin manhole. (±326’) Point “B5A” is a Type 1 catch basin which is the NDL for NDA 3. (±0-±33’) From Point “B5” to Point “B6”, runoff continues in a northerly direction as pipe flow via an 8” RCP. Did not observed. (±326’-±683’) Point “B6” is a Type 1 catch basin. (±683’) From Point “B6” to Point “A9”, runoff continues in a northerly direction as pipe flow via an 8” RCP. Did not observed. (±683-±735’) Point “A9” is a Type 2 catch basin manhole and the convergence point for the runoff for all NDAs From Point “A9” to Point “A10”, runoff is conveyed in a northerly direction as pipe flow via a 12” RCP. Did not observed (±735’-±823’). Point “A10” is the outfall to the Cedar River. The Cedar River flows northwest and eventually empties into Lake Washington. DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 2023 D. R. STRONG Consulting Engineers Inc. Page 31 Camellia Court Technical Information Report Renton, Washington TASK 5: MITIGATION OF EXISTING OR POTENTIAL PROBLEMS A review of the King County Water and Land Resources Division – Drainage Services Section Documented Drainage Complaints within one mile of the downstream flow paths has not shown any complaints within the last ten years. The project should not create any problems as specified in Section 1.2.2.1 of the Manual and therefore is not required to provide Drainage Problem Impact Mitigation subject to the requirements of Section 1.2.2.2. During construction, standard sediment and erosion control methods will be utilized. This will include the use of a stabilized construction entrance, perimeter silt fencing, and other necessary measures to minimize soil erosion during construction. DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 2023 D. R. STRONG Consulting Engineers Inc. Page 32 Camellia Court Technical Information Report Renton, Washington FIGURE 13 OFFSITE ANALYSIS DOWNSTREAM MAP DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 GRAPHIC SCALE 0 40 80 160 1 INCH = 80 FT. DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 2023 D. R. STRONG Consulting Engineers Inc. Page 33 Camellia Court Level One Downstream Analysis Renton, Washington FIGURE 14 OFFSITE ANALYSIS DOWNSTREAM TABLE DOWNSTREAM PATH 1 NDA 1 Symbol Drainage Component Type, Name, and Size Drainage Component Description Slope Distance From site Discharge Existing Problems Potential Problems Observations of field inspector resource reviewer, or resident See map Type: sheet flow, swale, Stream, channel, pipe, Pond; Size: diameter Surface area drainage basin, vegetation, cover, depth, type of sensitive area, volume % 1/4 mile = 1,320 feet Constrictions, under capacity, ponding, overtopping, flooding, habitat or organism destruction, scouring, bank sloughing, sedimentation, incision, other erosion Tributary area, likelihood of problem, overflow pathways, potential impacts. NDL 1 Natural discharge location for NDA 1 Runoff exits as sheet flow along the western property line of the northern portion of the Site. None Observed None Anticipated No concentrated flow observed A1 Type 1 CB (Catch Basin) None observed None anticipated Moderate flow observed A1-A2 Northerly pipe flow 8” PVC pipe ±0’-±222’ None Observed None Anticipated Did not observe A2 Type 1 CB ±222 None Observed None Anticipated Moderate flow observed A2-A3 Northerly pipe flow 8” PVC pipe –222’-±376’ None Observed None Anticipated Did not observe A3 Type 1 CB ±376’ None Observed None Anticipated Did not observe A3-A4 Westerly pipe flow 12” RCP (Reinforced Concrete Pipe) ±376’-±487’ None Observed None Anticipated Did not observe A4 Type 1 CB ±487’ None Observed None Anticipated Did not observe A4-A5 Westerly pipe flow 12” diameter RCP. ±487’-±516’ None Observed None Anticipated Did not observe A5 Type 2 CB manhole ±516’ None Observed None Anticipated Did not observe DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 2023 D. R. STRONG Consulting Engineers Inc. Page 34 Camellia Court Level One Downstream Analysis Renton, Washington A5-A6 Northerly Pipe flow 8” RCP ±587’-±609 None Observed None Anticipated Did not observe A6 Type 2 CB manhole ±609’ None Observed None Anticipated Did not observe A6-A7 Northerly pipe flow 8” RCP ±609’-±650’ None Observed None Anticipated Did not observe A7 Type 2 CB manhole ±650’ None Observed None Anticipated Did not observe A7-A8 Easterly pipe flow 8” RCP ±650’-±791’ None Observed None Anticipated Did not observe A8 Type 2 CB manhole ±791’ None Observed None Anticipated Did not observe A8-A9 Easterly pipe flow 8” RCP ±791’-±929’ None Observed None Anticipated Did not observe A9 Convergence point for the runoff from NDA 1 and NDA 2 Type 2 CB manhole ±929’ None Observed None Anticipated Did not observe A9-A10 Northerly pipe flow 12” RCP ±929’- ±1,017’ None Observed None Anticipated Did not observe A10 Cedar River pipe outfall ±1,017’ None Observed None Anticipated Did not observe DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 2023 D. R. STRONG Consulting Engineers Inc. Page 35 Camellia Court Level One Downstream Analysis Renton, Washington DOWNSTREAM PATH 2 NDA 2 Symbol Drainage Component Type, Name, and Size Drainage Component Description Slope Distance From site Discharge Existing Problems Potential Problems Observations of field inspector resource reviewer, or resident See map Type: sheet flow, swale, Stream, channel, pipe, Pond; Size: diameter Surface area drainage basin, vegetation, cover, depth, type of sensitive area, volume % 1/4 mile = 1,320 feet Constrictions, under capacity, ponding, overtopping, flooding, habitat or organism destruction, scouring, bank sloughing, sedimentation, incision, other erosion Tributary area, likelihood of problem, overflow pathways, potential impacts. NDL 2 Natural discharge location for NDA 2 Located along the southern property line in the southern portion of the Site. None Observed None Anticipated No concentrated flow observed B1 Collected roof runoff appears to be piped directly to this CB. Type 1 CB (Catch Basin) ±0 None Observed None Anticipated No concentrated flow observed B1-B2 Easterly pipe flow 8” DI pipe(Ductile Iron) ±0’-±67’ None Observed None Anticipated No concentrated flow observed B2 Type 1 CB ±67 None Observed None Anticipated Moderate flow observed B2-B3 Easterly pipe flow 8” DI pipe ±67’-±118” None Observed None Anticipated Did not observe B3 Type 1 CB ±118’ None Observed None Anticipated Did not observe B3-B4 Northerly pipe flow 8” RCP ±118’-±176’ None Observed None Anticipated Did not observe B4 Type 2 CB manhole ±176’ None Observed None Anticipated Did not observe B4-B5 Northerly pipe flow 8” RCP ±176’-±326’ None Observed None Anticipated Did not observe B5 Type 2 CB manhole ±326’ None Observed None Anticipated Did not observe B5A Type 1 CB ±0’-±33’ None Observed None Anticipated Did not observe B5-B6 Northerly pipe flow 8” RCP ±326’-±683’ None Observed None Anticipated Did not observe DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 2023 D. R. STRONG Consulting Engineers Inc. Page 36 Camellia Court Level One Downstream Analysis Renton, Washington B6 Type 1 CB ±683’ None Observed None Anticipated Did not observe B6-A9 Northerly pipe flow 8” RCP ±683’-±735’ None Observed None Anticipated Did not observe A9-A10 Northerly pipe flow 12” RCP ±735’-±823’ None Observed None Anticipated Did not observe A10 Cedar River pipe outfall ±823’ None Observed None Anticipated Did not observe DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 2023 D. R. STRONG Consulting Engineers Inc. Page 37 Camellia Court Technical Information Report Renton, Washington SECTION IV FLOW CONTROL ANALYSIS AND WATER QUALITY DESIGN EXISTING SITE HYDROLOGY The total existing Site area is approximately 17,262 s.f. (0.396 acres). The total Project area is 19,262 s.f. (0.439 acres), which includes the Site, the sidewalk area within Williams Avenue S ROW to be reconstructed and the proposed paving within the alley. The Site is currently developed with a single family home, a duplex, a multi-unit commercial building, concrete and gravel parking area, and landscaping. DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 2023 D. R. STRONG Consulting Engineers Inc. Page 38 Camellia Court Technical Information Report Renton, Washington FIGURE 15 PREDEVELOPED AREA MAP DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 0 GRAPHIC SCALE 15 30 45 1 INCH = 30 FT. DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 2023 D. R. STRONG Consulting Engineers Inc. Page 39 Camellia Court Technical Information Report Renton, Washington DEVELOPED SITE HYDROLOGY The applicant is seeking approval to develop three parcels totalling 0.396 acres into a 6- story, 95-unit residential building (Project). The proposed impervious surface areas are as follows: roof area of the proposed building, sidewalk, curb and gutter along Williams Ave S and paving along alley. The Project will generate approximately 18,976 s.f. of impervious area (0.436 acres). The Project is required to meet the City’s Peak Rate Flow Control Standard (Existing Conditions). The Site is required to “match the developed peak discharge rates to existing site conditions peak discharge rates for 2-, 10-, and 100-year return periods,” (2022 City of Renton Surface Water Design Manual, Sec. 1.2.3.1.A). However, the Project will result in less than an 0.15 CFS increase in the 100-year peak flow and therefore qualifies for an exception from providing a flow control facility. Existing 100-year peak runoff from the Site is 0.2123 CFS and the proposed 100-year peak runoff will be 0.3373 CFS, a difference of 0.1250 CFS. See appendix B for WWHM modeling results. Total new and replaced pollution generating surfaces (PGIS) will be 831 s.f., below the 5,000 s.f. threshold for requiring water quality treatment. See Section II CR#9 for discussion of flow control BMPs. DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 2023 D. R. STRONG Consulting Engineers Inc. Page 40 Camellia Court Technical Information Report Renton, Washington FIGURE 16 DEVELOPED AREA MAP DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 0 GRAPHIC SCALE 15 30 45 1 INCH = 30 FT. DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 2023 D. R. STRONG Consulting Engineers Inc. Page 41 Camellia Court Technical Information Report Renton, Washington SECTION V CONVEYANCE SYSTEM ANALYSIS AND DESIGN Per Core Requirement #4 of the KCSWDM, the conveyance system must be analyzed and designed for the existing tributary and developed onsite runoff. Pipe systems shall be designed to convey the 25-year storm with a minimum of 6-inches of freeboard between the design water surface and structure grate. Any overflow from the 100-year design storm must not create or aggravate a severe flooding problem. The Rational Method will be used to calculate the Q-Ratio for each pipe node. No onsite conveyance system is proposed for the Project. Roof runoff will be collected internally to the building and discharged to an existing catch basin located in the alley south of the building. The conveyance capacity of this connection will be considered during final engineering. DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 2023 D. R. STRONG Consulting Engineers Inc. Page 42 Camellia Court Technical Information Report Renton, Washington SECTION VI SPECIAL REPORTS AND STUDIES The following report and studies are included with this submittal. Geotechnical Engineering Study: Geotech Consultants, Inc – May 24, 2022 DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 May 24, 2022 JN 22149 GEOTECH CONSULTANTS, INC. Williams Avenue Ventures LLC 9219 Southeast 33rd Place Mercer Island, Washington98040 Attention: Leon Cohen via email: leon@leongcs.com Subject: Transmittal Letter – Geotechnical Engineering Study Proposed Camelia Court Apartment Building 99-107 Williams Avenue South Renton, Washington Dear Mr. Cohen, Attached to this transmittal letter is our geotechnical engineering report for the proposed Camelia Court Apartment Building to be constructed in Renton. The scope of our services consisted of exploring site surface and subsurface conditions, and then developing this report to provide recommendations for general earthwork and design considerations for foundations, retaining walls, subsurface drainage, and temporary excavations and shoring. This work was authorized by your acceptance of our proposal, P-11138, dated March 25, 2022. The attached report contains a discussion of the study and our recommendations. Please contact us if there are any questions regarding this report, or for further assistance during the design and construction phases of this project. Respectfully submitted, GEOTECH CONSULTANTS, INC. Marc R. McGinnis, P.E. Principal cc: Roger H. Newell Architect – Roger H. Newell via email: roger@rhnewellaia.com MKM/MRM:kg DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 GEOTECH CONSULTANTS, INC. GEOTECHNICAL ENGINEERING STUDY Proposed Camelia Court Apartment Building 99-107 Williams Avenue South Renton, Washington This report presents the findings and recommendations of our geotechnical engineering study for the site of the proposed Camelia Court Apartment building to be constructed in Renton. Development of the property is in the planning stage, and detailed plans were not available at the time of this study. The preliminary site plans provided to us were prepared by Roger H. Newell Architect, dated February 7, 2022. Based on these plans, and our discussions with Leon Cohen. We understand that a new, six story apartment building is proposed to be constructed at the subject property. The new building will be underlain by one story of underground parking, with a deep elevator pit. Additional parking will be available in the main floor. The remaining second through sixth floors will contain residential apartment units of varying square footage. A courtyard will be located atop the parking garage on the second floor in the western-central side of the building. Entrance to the parking garage will be from the western alley, and pedestrian access is proposed off the eastern street. No elevations have been proposed at this time, but we anticipate that excavations of at least 10 to 12 feet will be needed to reach the basement level foundations, with a deeper local excavation for the central elevator pit/building depending on its final design. Zero lot line setbacks are being proposed for the basement level parking garage on all four sides of the property. If the scope of the project changes from what we have described above, we should be provided with revised plans in order to determine if modifications to the recommendations and conclusions of this report are warranted. SITE CONDITIONS SURFACE The Vicinity Map, Plate 1, illustrates the general location of the site in the northern downtown area of Renton. The site is comprised of three contiguous parcels that form a rectangular-shaped lot with approximate dimensions of 150 feet in the north-south direction, and 115 feet in the east-west direction. The site is bordered to the north by a single-family parcel, to the east by Williams Avenue South, and to the south and west by an alleyway. Multi-story retirement living buildings lie both south and west of the alleyways. The grade across the three parcels is essentially flat, with only gentle declines within localized areas on each parcel. This is consistent with the topography in the surrounding area. The northern two parcels are developed with single-family residences located on the eastern sides of the lots. These residences are older in construction and are one to two stories in height. A one-story, commercial building is located on the southern parcel. Grass lawn and parking areas are set on the western half of he northern two lots, and on the western perimeter of the southern lot. The northern adjacent parcel is developed with a one-story residence that is underlain by a partial footprint basement. This residence appears to be set within 5 feet of the common property line at its closest. While streets and alleys line the remaining eastern, southern, and western sides of the property, newer multi story residential buildings are set south and west of the alley. The southern DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 Williams Avenue Ventures LLC JN 22149 May 24, 2022 Page 2 GEOTECH CONSULTANTS, INC. building is six stories in height, and it does not appear that this structure is underlain by a basement. Based on the limited permitting information available online, it would appear that this six-story building was recently constructed in 2018-2019, as older Google Streets images indicate that this building was once a one-story commercial structure similar to the small building on our site’s southernmost lot. The building to the west of the site is five stories in height and appears to contain one level of below grade parking. West of Williams Avenue South is the Fulton Apartments (110 Williams Avenue South). Our firm provided geotechnical services during the construction of this building in 2002. This building is underlain by a basement. Many of the older single-family residences in this area, including the residences on the subject property and adjacent to the north, have undergone variable levels of post-construction settlement over their lifespans. These homes, which do not have strengthened, modern foundations have visible signs to excessive settlement in the form of cracked foundations, dips of moderate in the roof, and out of level building materials. Many of the on-grade structures in the vicinity also show signs of settlement related distress. Some small cracks could also be observed in the exposed walls of the western apartment building. SUBSURFACE The subsurface conditions on the site were explored advancing three Cone Penetration Tests (CPTs) at the approximate locations shown on the Site Exploration Plan, Plate 2. Our exploration program was based on the proposed construction, anticipated subsurface conditions and those encountered during exploration, and the scope of work outlined in our proposal. The Cone Penetration Tests were advanced using a large, truck push rig on May 9, 2022. The data from the CPTs have been used to characterize the subsurface conditions beneath the site using empirical relations obtained from sensors at the tip of the CPT sounding probe. The CPT logs are attached to the end of this report as Plates 3 through 5. Our firm also completed the geotechnical study, as well as observation of the shoring installation, excavation, and foundation construction for the Fulton Apartments located to the east of the site at 110 Williams Avenue South. As a part of this study, we reviewed the explorations conducted for that project. Apparently, it has not been possible to obtain from the City of Renton the explorations that were completed for the retirement living facilities to the west and south of the site. Soil Conditions The CPTs were advanced on the western side of the site, within the gravel parking areas. CPT-1 and CPT-2 were advanced near the northwest and southwest corners of the site, and CPT-3 was advanced in the approximate central-western edge of the site. Beneath the ground surface, loose alluvial silt and sand was revealed, containing scattered organic layers. This upper, loose soil layer continued to a depth of 10 to 16 feet, where medium- dense sand and gravel was revealed. This sand and gravel layer was observed to be highly variable in density, exhibiting a medium-dense and denser constancy in CPT-1 and CPT-2. The deepest looser surficial deposits were revealed in CPT-3, located in the center of the site, where medium-dense soils were not revealed until 16 feet. The medium-dense and denser alluvial sand and gravel continued to the base of the three CPTs at depths of 25 to 36 feet where refusal was met. DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 Williams Avenue Ventures LLC JN 22149 May 24, 2022 Page 3 GEOTECH CONSULTANTS, INC. The site and surrounding vicinity of Downtown Renton are underlain by a variable layer of unconsolidated, alluvial soils, which are soils that were deposited by flowing water. The alluvium becomes very gravelly and coarse grained typically within 8 to 15 feet of the ground surface. Like most alluvial deposits, the soil beneath the site contains variable soil layers, containing large cobbles and boulders, and occasional organics. As evidenced in the CPTs, it is common to find looser layers within the more alluvial sand and gravel. These layers can be discontinuous and localized depending on the water flow velocities that occurred during the soil’s deposition. Generally similar soil conditions were encountered in our previous borings conducted for the Fulton Apartments to the west. The coarse-grained gravels were 8 to 12 feet below existing grade on the west side of that property, closest to the subject site. Obstructions in the form of cobbles were revealed by our explorations and can be observed by spikes in the CPT readings. These obstructions made advancing the cone rods excessively difficult and led to refusal in all three exploration locations. However, debris, buried utilities, and old foundation and slab elements are commonly encountered on sites that have had previous development. Cobbles and boulders are often found in soils that have been deposited by glaciers or fast- moving water. Groundwater Conditions Groundwater seepage was recorded at a depth of 16 feet in all three exploration locations. This groundwater table is determined by pore pressure measurements on the CPT probe, so can be somewhat inaccurate. However, based on our previous work on the adjacent Fulton Apartments site, we expect seasonal high groundwater to lie at 15 to 16 feet below the ground surface. It should be noted that groundwater levels vary seasonally with rainfall and other factors. We anticipate that groundwater could be found in more permeable soil layers. The stratification lines on the logs represent the approximate boundaries between soil types at the exploration locations. The actual transition between soil types may be gradual, and subsurface conditions can vary between exploration locations. The logs provide specific subsurface information only at the locations tested. The relative densities and moisture descriptions indicated on the CPT logs are empirical correlations based on the conditions observed with the sensory equipment during the explorations. CONCLUSIONS AND RECOMMENDATIONS GENERAL THIS SECTION CONTAINS A SUMMARY OF OUR STUDY AND FINDINGS FOR THE PURPOSES OF A GENERAL OVERVIEW ONLY. MORE SPECIFIC RECOMMENDATIONS AND CONCLUSIONS ARE CONTAINED IN THE REMAINDER OF THIS REPORT. ANY PARTY RELYING ON THIS REPORT SHOULD READ THE ENTIRE DOCUMENT. The explorations conducted for this study encountered alluvial silt, sand, and gravel, which is typical for this area of Renton. The surficial 10 to 16 feet of this soil is in a loose/soft state, and the alluvial DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 Williams Avenue Ventures LLC JN 22149 May 24, 2022 Page 4 GEOTECH CONSULTANTS, INC. soils generally became medium-dense and coarse grained beneath depths of 10 to 14 feet in CPT- 1 and CPT-2, and not until a depth of 16 feet in CPT-3. These medium-dense soils generally continued with depth, becoming medium-dense and denser in layers with depth. Current structures in the surrounding area that have been supported in typical conventional shallow foundation systems atop the surficial, looser alluvial soils can experience significant amounts of post-construction settlement due to consolidation of these loose soils over time. Furthermore, the soil in this area that is below the groundwater table is susceptible to liquefaction during a large seismic event. Considering the anticipated excavation depths of more than 10 feet, medium-dense sand and gravel should be encountered at, or close to, the base of much of the excavation, and a heavily reinforced mat foundation can be used for the support of the planned building. A mat foundation is essentially a heavily-reinforced, slab foundation that is intended to distribute the building loads, reduce the necessary bearing capacity, bridge over any excessively soft areas of soil or localized soil liquefaction (sand boils) and reduce the amount of differential settlement across the building. The mat foundation can be placed directly on top of the coarse-grained alluvium, after the excavated surface has been recompacted. Where loose/soft soils are encountered at the planned excavation level, they should be removed and be replaced with compacted granular soils. In wet conditions, this structural fill would likely need to consist of clean crushed rock, such as ballast rock, or 2 to 4-inch quarry spalls. This clean, open-graded rock can be easily placed and compacted without the need for vibratory compaction equipment. The construction budget should contain a contingency for the additional potential cost of overexcavation and replacement. The base of the excavation should be assessed by the project geotechnical engineer to assess whether or not unsuitable soils need to be removed and replaced with structural fill. Additional recommendations can be found in the Mat Foundations section of this report. If only a shallow excavation is proposed later in the design, or the anticipated building loads will be too great to spread out across a lightly loaded mat foundation, deep foundation systems will need to be used to support the new building. In this area, augercast concrete piles are typically used to accomplish this. Preliminary augercast pile recommendations are provided below, but we can provide further recommendations regarding this as the design progresses. Excavations of at least 10 feet are anticipated to be needed to reach the basement level parking garage across all four sides of the site. Based on the zero-lot line setbacks, the excavation depth, poor surficial soils, and the presence of nearby structures and roadways, we expect that excavation shoring will need to be utilized on all four sides of the excavation. For this project, the only appropriate shoring method will be to use a rigid, drilled soldier pile shoring system. Some of the adjacent structures, and the adjacent roadways and utilities rest on loose soils and appear to have undergone varying levels settlement in the past. The shoring design must consider the potential risk of causing additional settlement in these existing, at-risk structures. Due to the high variability in the site soils, and the need to limit shoring deflections, the shoring system should be designed as rigid to the point where little to no deflections are anticipated while the excavation is open during construction of the basement. The shoring system should also be designed with the consideration that overexcavations may need to occur in front of the shoring piles to expose competent medium- dense sand and gravel. Where overexcavation is attempted near the perimeter foundations, it will be necessary to excavate the unsuitable soils one-bucket width at a time, immediately backfilling each overexcavated section with compacted quarry spalls or ballast rock. Refer to the section entitled Temporary Shoring for more information regarding design and installation of the proposed shoring. Based on the soil encountered in our explorations, and from previous construction experience in the vicinity, the site soils should not be excavated at an inclination steeper than a 1.5:1 DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 Williams Avenue Ventures LLC JN 22149 May 24, 2022 Page 5 GEOTECH CONSULTANTS, INC. (Horizontal:Vertical) extending continuously from top to bottom of a cut. Even at this relatively flat inclination, the loose, uncompressed alluvial soils have an elevated caving potential, and flatter inclinations may be needed where perched seepage, or caving occurs. Vertical excavations should not be attempted, and instability was encountered in temporary cut slopes attempted at a 1:1 (H:V) inclination for the Fulton Apartments project. Ecology blocks, or similar non-structural shoring, will not be sufficient to hold up the loose near-surface soils in vertical excavations. In general, unshored excavations should not extend beneath a 3:1 (H:V) line drawn extending downward from any adjacent foundation, utility, or right-of-way. We also anticipate that the deep excavation for the elevator pit will also need to be shored to prevent caving within the excavation. The adjacent older buildings, such as the house to the immediate north of the site, are likely supported on conventional foundations that bear on compressible soils. As a result, it is likely that they have undergone excessive settlement already. It will be important to determine the foundation design for the newer building to the south. There is always some risk associated with demolition and foundation construction near structures such as this. It is imperative that unshored excavations do not extend below a 3:1 (Horizontal:Vertical) imaginary bearing zone sloping downward from existing footings. Contractors working on the demolition and construction of the new rowhouses must be cautioned to avoid strong ground vibrations, which could cause additional settlement in the neighboring foundations. During demolition, strong pounding on the ground with the excavator, which is often used to break up debris and concrete, should not occur. Large equipment and vibratory compactors should not be used close to the property lines or during large fill compaction operations due to the potential for sustained vibrations to adversely affect the neighboring structures and utilities. Additionally, in order to protect yourselves from unsubstantiated damage claims from the adjacent owners, 1) the existing condition of the foundation should be documented before starting demolition, and 2) the footings should be monitored for vertical movement during the demolition, excavation, and construction process. These are common recommendations for projects located close to existing structures that may bear on loose soil and have already experienced excessive settlement. We can provide additional recommendations for documentation and monitoring of the adjacent structures, if desired. The loose/soft alluvial soils are highly variable in composition, are fine-grained and silty, and contain varying organics. Based on this, and the size of the building, the onsite soils should not be used for any structural fill application at this site, as they will not be able to be adequately compacted and will be in an elevated moisture state. Fill beneath foundations must consist of an angular, clean rock such as quarry spalls or ballast rock, and free-draining granular fill should be used behind backfilled walls. Infiltration or dispersion systems should also not be explored for feasibility at this project due to the presence of basement spaces on and around the site, the composition of the subsurface soils, and the lack of open space to install such a system. All collected stormwater runoff should be tightlined offsite to the appropriate facilities. The lowest floor slab elevation should be set at least 2 feet above the encountered groundwater seepage level, and should be higher than that if possible. This provides added protection against unexpected high groundwater levels causing seepage into the basement garage. Regardless, underslab drainage should be provided below the mat slab. This is redundant protection to prevent a build-up of groundwater beneath the mat foundation in the event of seasonal groundwater fluctuations, which could impart hydrostatic uplift pressures on the foundations. It is likely that deeper penetrations, such as an elevator pit, would need to be of watertight construction. The erosion control measures needed during the site development will depend heavily on the weather conditions that are encountered. We anticipate that a silt fence will be needed around the downslope sides of any cleared areas. The need for a silt fence will be eliminated as soon as the DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 Williams Avenue Ventures LLC JN 22149 May 24, 2022 Page 6 GEOTECH CONSULTANTS, INC. excavation is below the surrounding grade. Existing pavements, ground cover, and landscaping should be left in place wherever possible to minimize the amount of exposed soil. Rocked staging areas and construction access roads should be provided to reduce the amount of soil or mud carried off the property by trucks and equipment. Trucks should not be allowed to drive off of the rock-covered areas. Cut slopes and soil stockpiles should be covered with plastic during wet weather. Onsite water containment, such as a Baker Tank, or specialty discharge permits may be needed to contain onsite water that accumulates within the excavation. Following clearing or rough grading, it may be necessary to mulch or hydroseed bare areas that will not be immediately covered with landscaping or an impervious surface. On most construction projects, it is necessary to periodically maintain or modify temporary erosion control measures to address specific site and weather conditions. The drainage and/or waterproofing recommendations presented in this report are intended only to prevent active seepage from flowing through concrete walls or slabs. Even in the absence of active seepage into and beneath structures, water vapor can migrate through walls, slabs, and floors from the surrounding soil, and can even be transmitted from slabs and foundation walls due to the concrete curing process. Water vapor also results from occupant uses, such as cooking, cleaning, and bathing. Excessive water vapor trapped within structures can result in a variety of undesirable conditions, including, but not limited to, moisture problems with flooring systems, excessively moist air within occupied areas, and the growth of molds, fungi, and other biological organisms that may be harmful to the health of the occupants. The designer or architect must consider the potential vapor sources and likely occupant uses, and provide sufficient ventilation, either passive or mechanical, to prevent a build up of excessive water vapor within the planned structure. As with any project that involves demolition of existing site buildings and/or extensive excavation and shoring, there is a potential risk of movement on surrounding properties. This can potentially translate into noticeable damage of surrounding on-grade elements, such as foundations and slabs. However, the demolition, shoring, and/or excavation work could just translate into perceived damage on adjacent properties. Unfortunately, it is becoming more and more common for adjacent property owners to make unsubstantiated damage claims on new projects that occur close to their developed lots. Therefore, we recommend making an extensive photographic and visual survey of the project vicinity, prior to demolition activities, installing shoring, and/or commencing with the excavation. This documents the condition of buildings, pavements, and utilities in the immediate vicinity of the site in order to avoid, and protect the owner from, unsubstantiated damage claims by surrounding property owners. Additionally, any adjacent structures should be monitored during demolition and construction to detect soil movements. To monitor their performance, we recommend establishing a series of survey reference points to measure any horizontal deflections of the shoring system. Control points should be established at a distance well away from the walls and slopes, and deflections from the reference points should be measured throughout construction by survey methods. Geotech Consultants, Inc. should be allowed to review the final development plans to verify that the recommendations presented in this report are adequately addressed in the design. Such a plan review would be additional work beyond the current scope of work for this study, and it may include revisions to our recommendations to accommodate site, development, and geotechnical constraints that become more evident during the review process. We recommend including this report, in its entirety, in the project contract documents. This report should also be provided to any future property owners so they will be aware of our findings and recommendations. DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 Williams Avenue Ventures LLC JN 22149 May 24, 2022 Page 7 GEOTECH CONSULTANTS, INC. SEISMIC CONSIDERATIONS In accordance with the International Building Code (IBC), the site class within 100 feet of the ground surface would best be represented by Site Class Type F (Failure Prone Site Class), due to its liquefiable nature. However, ASCE 7 allows for an exception from the F classification if the building period is less than 0.5 seconds. If the building period falls beneath this threshold, a Site Class E can be used for this project. As noted in the USGS website, the mapped spectral acceleration value for a 0.2 second (Ss) and 1.0 second period (S1) equals 1.44g and 0.49g, respectively. If the building period is found to be in excess of 0.5 seconds, a site-specific seismic analysis and study would need to be completed by a specialty consultant, as the ASCE does not allow any other exceptions for larger buildings in liquefiable soils. The soils that will support the building are coarse-grained and in a medium-dense to dense condition. The IBC and ASCE 7 require that the potential for liquefaction (soil strength loss) be evaluated for the peak ground acceleration of the Maximum Considered Earthquake (MCE) which has a probability of occurring once in 2,475 years (2 percent probability of occurring in a 50-year period). The MCE peak ground acceleration adjusted for site class effects (FPGA) equals 0.67g. Current geotechnical analysis cannot accurately predict where and to what extent soil liquefaction will occur during a large earthquake. Using procedures developed by Seed, Idress, et al., it is possible that the coarse-grained soils below the groundwater table could liquefy. While the potential for this to occur in very gravelly soils is thought to be lower than for finer-grained sands. Even so, we have calculated the approximate total ground settlement that could result if liquefaction were to occur in the saturated, loose to medium-dense soils as a result of the design earthquake for this site, and for nearby projects in the Renton Valley. Based on these analyses, it is possible that soil liquefaction could occur at the site during the MCE with total calculated ground settlement in the order of up to 4 to 6 inches. The potential for excessive differential settlement across the structure will be mitigated by the mat foundations such that we would predict differential dynamic settlements of 2 to 4 inches across the structure in the event of a large earthquake. Sections 1803.5 of the IBC and 11.8 of ASCE 7 require that other seismic-related geotechnical design parameters (seismic surcharge for retaining wall design and slope stability) include the potential effects of the Design Earthquake. The peak ground acceleration for the Design Earthquake is defined in Section 11.2 of ASCE 7 as two-thirds (2/3) of the MCE peak ground acceleration, or 0.45g. The recommendations for a mat foundation system presented in this report are intended to prevent catastrophic foundation collapse during a large seismic event. By preventing catastrophic settlement of the foundations, the safety of the occupants should be protected. The intent is not to prevent damage or ensure continued function of the structures after the design seismic event. MAT FOUNDATIONS The mat foundation should be supported on the coarse-grained gravelly alluvial after it has been recompacted. As discussed in the General section, some overexcavation and replacement will likely be necessary to remove loose/soft soils remaining after the excavation is completed. An allowable bearing pressure of 2,000 pounds per square foot (psf) should be used for the mat foundation design. A one-third increase in this design bearing pressure may be used when considering short-term wind or seismic loads. DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 Williams Avenue Ventures LLC JN 22149 May 24, 2022 Page 8 GEOTECH CONSULTANTS, INC. Mat foundations are typically designed using the appropriate flexible method. Foundations designed using this method are also known as Winkler Foundations. For this analysis, we recommend using a coefficient of subgrade reaction of 90 pounds per cubic inch (lb/in3). Any shallow mat slabs should be thickened a minimum depth of 18 inches below the adjacent finish grade around the perimeter of the mat, and this thickened edge of the structural slabs should have a minimum width of 16 inches. Deflections will depend on the stiffness of the slab, but we anticipate total deflections under static conditions over time to be on the order of 2 to 3 inches and differential settlements across the structure on the order of 1 to 2 inches or less, can be anticipated. Lateral loads due to wind or seismic forces may be resisted by friction between the foundations and the bearing soil, or by passive pressure acting on the vertical, embedded portions of the foundation. For the latter condition, the foundation must be either poured directly against relatively level, undisturbed soil or be surrounded by level, well-compacted fill. We recommend using the following ultimate values for the foundation’s resistance to lateral loading. PARAMETER ULTIMATE VALUE Coefficient of Friction 0.40 Passive Earth Pressure 250 pcf Where: pcf is Pounds per Cubic Foot, and Passive Earth Pressure is computed using the equivalent fluid density. If the ground in front of a foundation is loose or sloping, the passive earth pressure given above will not be appropriate. We recommend maintaining a safety factor of at least 1.5 for the foundation’s resistance to lateral loading when using the above ultimate values. AUGERCAST CONCRETE PILES Augercast piles are installed using continuous flight, hollow-stem auger equipment mounted on a crane. Concrete grout must be pumped continuously through the auger as it is withdrawn. This allows the piles to be installed where caving conditions or significant groundwater are anticipated. We recommend that augercast piles be installed by an experienced contractor who is familiar with the anticipated subsurface conditions. An allowable compressive capacity of 30 tons can be attained by installing a 16-inch-diameter, augercast concrete pile at least 10 feet into the medium-dense and denser sand and gravel. For transient loading, such as wind or seismic loads, the allowable pile capacity may be increased by one-third. We can provide design criteria for different pile diameters and embedment lengths, if greater capacities are required. The minimum center-to-center pile spacing should be three times the pier diameter to prevent a reduction in the individual pile compressive capacity. Based on our subsurface information information, we estimate that pile lengths of about 25 to 35 feet below the existing grade would be required to achieve adequate penetration into the medium-dense and denser sand and gravel. This estimated depth will be influenced by the final foundation elevations and required structural demands of the piles. This above compressive capacity does not include the potential downdrag forces that may occur within the soil located above the groundwater table in the event of a seismic-induced liquefaction. This force will vary depending on the excavation depth as well as the pile depths. We can comment DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 Williams Avenue Ventures LLC JN 22149 May 24, 2022 Page 9 GEOTECH CONSULTANTS, INC. on downdrag forces during the preliminary pile design and once a bottom of excavation elevation has been determined. We estimate that the total settlement of single piles installed as described above will be on the order of one inch. Most of this settlement should occur during the construction phase as the dead loads are applied. The remaining post-construction settlement would be realized as the live loads are applied. We estimate that differential settlements between the foundation piles over any portion of the structures should be less than about one-half-inch. We recommend reinforcing each pile its entire length. This typically consists of a rebar cage extending a portion of the pile’s length with a full-length center bar. Each pile can be assumed to have a point of fixity (point of maximum bending moment) at 15 feet below the top of the pile for design of the reinforcing. Passive earth pressures on the grade beams will also provide some lateral resistance. If structural fill is placed against the outside of the grade beams, the design passive earth pressure from the fill can be assumed to be equal to that pressure exerted by an equivalent fluid with a density of 300 pcf. This passive resistance is an ultimate value that does not include a safety factor. Augercast Pile Installation This section provides general, and typically minimum, guidelines for installation of augercast concrete piles. The piles should be installed by a contractor with experience in the successful installation of augercast piles, in similar soil and groundwater conditions. The piles should be installed with continuous-flight hollow stem auger equipment specifically designed for the installation of auger-placed grout-injected piles. The grout injection point should be at the tip of the auger bit, below the cutting teeth. Due to potential variability in soil conditions on any site, the contractor should provide sufficient auger length to extend the piles well beyond the lengths estimated above and/or indicated by the available exploration information. The following are general accepted techniques that are typically used by local experienced contractors: • The grout should be placed under a minimum pressure of 200 pounds per square inch (psi) to provide adequate bonding with the bearing soils. A pressure gauge should be installed on or near the pump to monitor the pressures during the grouting. The gauge should be easily accessible to the field technician. • A mechanical counter should be located on the grout pump to record the number of strokes required for installation of each pile. • The grout pump should be calibrated prior to pile installation by pumping grout into a container of known volume. This procedure should be repeated as often as deemed necessary to provide a reasonable calibration by the field technician. • Each pile should be drilled and completely filled with grout in an uninterrupted operation. The auger hoisting equipment should be capable of withdrawing the auger smoothly and at a constant rate without jumps or stops. The auger should be removed slowly and smoothly to maintain a constant pressure during removal. A positive grout head of at least 5 feet should be maintained at all times to prevent caving of the drilled hole and the formation of voids. If the removal becomes erratic, or if there is a sudden drop in grout pressure, the pile should be redrilled at least 5 feet below the level when the grout pressure dropped prior to resuming withdrawal. DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 Williams Avenue Ventures LLC JN 22149 May 24, 2022 Page 10 GEOTECH CONSULTANTS, INC. • Clockwise rotation of the auger should be performed during the grouting process at least until the grout flow is observed out of the top of the drilled hole. This will stabilize the sides and facilitate spoil material removal. • The installation of piles located within 6 pile diameters of each other on the same working day is not recommended, and piles must cure 24 hours before installation of adjacent piles. • The fresh grout will subside, usually within the first 2 hours. If the grout has not set, the pile should be topped off with fresh grout to the cutoff elevation. • Augercast piles may be reinforced with single or bundled steel reinforcing rods or reinforcing bar cages. The reinforcing should be inserted before the grout sets. The reinforcing should be installed plumb and centered in the pile to avoid contact with the soil. Also, each pile should include a full-length, steel rod in the center; this will serve as a probe to determine the continuity of the pile. Pile Installation Observation A representative of project geotechnical engineer should observe the pile installation process on a full-time basis. The monitoring should include collecting and interpreting the installation data and verifying the bearing stratum elevations. FOUNDATION AND RETAINING WALLS Retaining walls backfilled on only one side should be designed to resist the lateral earth pressures imposed by the soil they retain. The following recommended parameters are for walls that restrain level backfill: PARAMETER VALUE Lateral Earth Pressure * At Rest Earth Pressure 45 pcf 60 pcf Passive Earth Pressure 250 pcf Coefficient of Friction 0.40 Soil Unit Weight 130 pcf Where: pcf is Pounds per Cubic Foot, and Lateral and Passive Earth Pressures are computed using the Equivalent Fluid Pressures. * For a restrained wall that cannot deflect at least 0.002 times its height, a uniform lateral pressure equal to 10 psf times the height of the wall should be added to the above lateral equivalent fluid pressure. This applies only to walls with level backfill. The design values given above do not include the effects of any hydrostatic pressures behind the walls and assume that no surcharges, such as those caused by slopes, vehicles, or adjacent foundations will be exerted on the walls. If these conditions exist, those pressures should be added to the above lateral soil pressures. Where sloping backfill is desired behind the walls, we will need to be given the wall dimensions and the slope of the backfill in order to provide the appropriate design earth pressures. The surcharge due to traffic loads behind a wall can typically be accounted for by adding a uniform pressure equal to 2 feet multiplied by the above lateral fluid density. Heavy construction equipment should not be operated behind retaining and foundation walls within a DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 Williams Avenue Ventures LLC JN 22149 May 24, 2022 Page 11 GEOTECH CONSULTANTS, INC. distance equal to the height of a wall, unless the walls are designed for the additional lateral pressures resulting from the equipment. The values given above are to be used to design only permanent foundation and retaining walls that are to be backfilled, such as conventional walls constructed of reinforced concrete or masonry. It is not appropriate to use the above earth pressures and soil unit weight to back-calculate soil strength parameters for design of other types of retaining walls, such as soldier pile, reinforced earth, modular or soil nail walls. We can assist with design of these types of walls, if desired. The passive pressure given is appropriate only for a shear key poured directly against undisturbed native soil, or for the depth of level, well-compacted fill placed in front of a retaining or foundation wall. The values for friction and passive resistance are ultimate values and do not include a safety factor. Restrained wall soil parameters should be utilized the wall and reinforcing design for a distance of 1.5 times the wall height from corners or bends in the walls, or from other points of restraint. This is intended to reduce the amount of cracking that can occur where a wall is restrained by a corner. Wall Pressures Due to Seismic Forces Per IBC Section 1803.5.12, a seismic surcharge load need only be considered in the design of walls over 6 feet in height. A seismic surcharge load would be imposed by adding a uniform lateral pressure to the above-recommended lateral pressure. The recommended seismic surcharge pressure for this project is 9H pounds per square foot (psf), where H is the design retention height of the wall. Using this increased pressure, the safety factor against sliding and overturning can be reduced to 1.2 for the seismic analysis. Retaining Wall Backfill and Waterproofing Backfill placed behind retaining or foundation walls should be coarse, free-draining structural fill containing no organics. This backfill should contain no more than 5 percent silt or clay particles and have no gravel greater than 4 inches in diameter. The percentage of particles passing the No. 4 sieve should be between 25 and 70 percent. The free-draining backfill should be hydraulically connected to the foundation drain system. Free draining backfill should be used for the entire width of the backfill where seepage is encountered. For increased protection, drainage composites should be placed along cut slope faces, and the walls should be backfilled entirely with free-draining soil. The later section entitled Drainage Considerations should also be reviewed for recommendations related to subsurface drainage behind foundation and retaining walls. The purpose of these backfill requirements is to ensure that the design criteria for a retaining wall are not exceeded because of a build-up of hydrostatic pressure behind the wall. Also, subsurface drainage systems are not intended to handle large volumes of water from surface runoff. The top 12 to 18 inches of the backfill should consist of a compacted, relatively impermeable soil or topsoil, or the surface should be paved. The ground surface must also slope away from backfilled walls at one to 2 percent to reduce the potential for surface water to percolate into the backfill. Water percolating through pervious surfaces (pavers, gravel, permeable pavement, etc.) must also be prevented from flowing toward walls or into the backfill zone. Foundation drainage and waterproofing systems are not intended to handle large volumes of infiltrated water. The compacted subgrade below pervious surfaces and any associated drainage layer DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 Williams Avenue Ventures LLC JN 22149 May 24, 2022 Page 12 GEOTECH CONSULTANTS, INC. should therefore be sloped away. Alternatively, a membrane and subsurface collection system could be provided below a pervious surface. It is critical that the wall backfill be placed in lifts and be properly compacted, in order for the above-recommended design earth pressures to be appropriate. The recommended wall design criteria assume that the backfill will be well-compacted in lifts no thicker than 12 inches. The compaction of backfill near the walls should be accomplished with hand- operated equipment to prevent the walls from being overloaded by the higher soil forces that occur during compaction. The section entitled General Earthwork and Structural Fill contains additional recommendations regarding the placement and compaction of structural fill behind retaining and foundation walls. The above recommendations are not intended to waterproof below-grade walls, or to prevent the formation of mold, mildew, or fungi in interior spaces. Over time, the performance of subsurface drainage systems can degrade, subsurface groundwater flow patterns can change, and utilities can break or develop leaks. Therefore, waterproofing should be provided where future seepage through the walls is not acceptable. This typically includes limiting cold-joints and wall penetrations and using bentonite panels or membranes on the outside of the walls. There are a variety of different waterproofing materials and systems, which should be installed by an experienced contractor familiar with the anticipated construction and subsurface conditions. Applying a thin coat of asphalt emulsion to the outside face of a wall is not considered waterproofing and will only help to reduce moisture generated from water vapor or capillary action from seeping through the concrete. As with any project, adequate ventilation of basement and crawl space areas is important to prevent a buildup of water vapor that is commonly transmitted through concrete walls from the surrounding soil, even when seepage is not present. This is appropriate even when waterproofing is applied to the outside of foundation and retaining walls. We recommend that you contact an experienced envelope consultant if detailed recommendations or specifications related to waterproofing design or minimizing the potential for infestations of mold and mildew are desired. TEMPORARY SHORING Given the poor soil conditions, excavation depths, zero-lot line setbacks, and presence of nearby settlement sensitive structures, shoring will be needed on all four sides of the excavation. For this project, the only appropriate shoring method that will provide the necessary rigidity to limit deflections in the excavation will be to use drilled, soldier piles. These soldier piles will need to be designed to limit the magnitude and occurrence of any deflections within the retained height of the cut to prevent adversely impacting the adjacent streets, utilities, and buildings. This will be particularly important near the adjacent northern residence. In general, we recommend a maximum 6-foot center-to-center pile spacing, in order to reduce the potential for excessive caving in the loose near-surface soils during excavation and lagging placement. Soldier pile walls would be constructed after making planned cut slopes, and prior to commencing the mass excavation, by setting steel H-beams in a drilled hole and grouting the space between the beam and the soil with concrete for the entire height of the drilled hole. Wet, caving conditions will be encountered in the holes, and the contractor should be prepared to case the holes and/or use the slurry method if caving soil is encountered. Excessive ground loss in the drilled holes must be DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 Williams Avenue Ventures LLC JN 22149 May 24, 2022 Page 13 GEOTECH CONSULTANTS, INC. avoided to reduce the potential for settlement on adjacent properties. If water is present in a hole at the time the soldier pile is poured, concrete must be tremied to the bottom of the hole. Augercast or Continuous Flight Auger (CFA) drilling methods may also be used if the contractor has these methods available to them. As the excavation proceeds downward, the space between the piles should be lagged with timber, and any voids behind the timbers should be filled with Controlled Density Fill (CDF). Treated lagging is usually required for permanent walls, while untreated lagging can often be utilized for temporary shoring walls. Temporary vertical cuts will be necessary between the soldier piles for the lagging placement. The prompt and careful installation of lagging is important, particularly in loose or caving soil, to maintain the integrity of the excavation and provide safer working conditions. Additionally, care must be taken by the excavator to remove no more soil between the soldier piles than is necessary to install the lagging. Caving or overexcavation during lagging placement could result in loss of ground on neighboring properties. Timber lagging should be designed for an applied lateral pressure of 30 percent of the design wall pressure if the pile spacing is less than three pile diameters. For larger pile spacings, the lagging should be designed for 50 percent of the design load. Soldier Pile Wall Design Temporary or permanent soldier pile shoring that is cantilevered should be designed for an active soil pressure equal to that pressure exerted by an equivalent fluid with a unit weight of 45 pounds per cubic foot (pcf). The active pressures should extend to at least 2 feet below the bottom of the excavation to account for the potential need for overexcavations to expose competent soil. If shoring will be located within a 2:1 (H:V) zone of the footings of the neighboring northern house or near any other potentially settlement sensitive structure, roadway, or utility, it should be designed for an at-rest earth pressure of 60 pcf in order to create a stiffer soldier pile system and to minimize the lateral movement of the shoring in these areas. An additional surcharge will need to be incorporated in the shoring design within the extent of this neighboring structure. The design/depth of the foundations for the building to the south need to be determined, in order to assess whether or not a surcharge needs to be included for the effect of that building’s foundations. Traffic surcharges adjacent to pavements travelled by trucks, such as garbage trucks, can typically be accounted for by increasing the effective height of the shoring wall by 3 feet. Heavier loads, such as those from concrete trucks, concrete pump trucks, large excavation equipment, etc. can create larger surcharge pressures on a shoring system. We can provide appropriate surcharge loads once more detailed plans have been developed. Any temporary cut slopes above the shoring walls will exert additional surcharge pressures. These surcharge pressures will vary, depending on the configuration of the cut slope and shoring wall. We can provide recommendations regarding slope and retaining wall surcharge pressures when the preliminary shoring design is completed. It is important that the shoring design provides sufficient working room to drill and install the soldier piles, without needing to make unsafe, excessively steep temporary cuts. Cut slopes should be planned to intersect the backside of the drilled holes, not the back of the lagging. Lateral movement of the soldier piles below the excavation level will be resisted by an ultimate passive soil pressure equal to that pressure exerted by a fluid with a density of 300 DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 Williams Avenue Ventures LLC JN 22149 May 24, 2022 Page 14 GEOTECH CONSULTANTS, INC. pcf. No safety factor is included in the given value. This soil pressure is valid only for a level excavation in front of the soldier pile; it acts on two times the grouted pile diameter. This passive pressure should not be assumed to begin until at least 2 feet below the bottom of the excavation to account for the potential for overexcavations to be needed in front of the piles. Cut slopes made in front of shoring walls significantly decrease the passive resistance. This includes temporary cuts necessary to install internal braces or rakers. The minimum embedment below the floor of the excavation for cantilever soldier piles should be equal to the height of the "stick-up." EXCAVATION AND SHORING MONITORING As with any shoring system, there is a potential risk of greater-than-anticipated movement of the shoring and the ground outside of the excavation. This can translate into noticeable damage of surrounding on-grade elements, such as foundations and slabs. Therefore, we recommend making an extensive photographic and visual survey of the project vicinity, prior to demolition activities, installing shoring or commencing excavation. This documents the condition of buildings, pavements, and utilities in the immediate vicinity of the site in order to avoid, and protect the owner from, unsubstantiated damage claims by surrounding property owners. Additionally, the shoring walls and any adjacent foundations should be monitored during construction to detect vertical movement. To monitor their performance, we recommend establishing a series of survey reference points to measure any horizontal deflections of the shoring system. Control points should be established at a distance well away from the walls and slopes, and deflections from the reference points should be measured throughout construction by survey methods. At least every other soldier pile should be monitored by taking readings at the top of the pile. Additionally, benchmarks installed on the surrounding buildings should be monitored for at least vertical movement. We suggest taking the readings at least once a week, until it is established that no deflections are occurring. The initial readings for this monitoring should be taken before starting any demolition or excavation on the site. EXCAVATIONS AND SLOPES Appropriate temporary cut slope inclinations for excavations above the water table are discussed in the General section. The recommended temporary slope inclination is based on the conditions exposed in our explorations, and on what has been successful at other sites with similar soil conditions. It is possible that variations in soil and groundwater conditions will require modifications to the inclination at which temporary slopes can stand. Temporary cuts are those that will remain unsupported for a relatively short duration to allow for the construction of foundations, retaining walls, or utilities. Temporary cut slopes should be protected with plastic sheeting during wet weather. It is also important that surface runoff be directed away from the top of temporary slope cuts. Cut slopes should also be backfilled or retained as soon as possible to reduce the potential for instability. Please note that loose soil can cave suddenly and without warning. Excavation, foundation, and utility contractors should be made especially aware of this potential danger. These recommendations may need to be modified if the area near the potential cuts has been disturbed in the past by utility installation, or if settlement-sensitive utilities are located nearby. DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 Williams Avenue Ventures LLC JN 22149 May 24, 2022 Page 15 GEOTECH CONSULTANTS, INC. Water should not be allowed to flow uncontrolled over the top of any temporary or permanent slope. All permanently exposed slopes should be seeded with an appropriate species of vegetation to reduce erosion and improve the stability of the surficial layer of soil. DRAINAGE CONSIDERATIONS We anticipate that permanent foundation walls will be constructed against the shoring walls due to the limited lot line setbacks. Where this occurs, a plastic-backed drainage composite, such as Miradrain, Battledrain, or similar, should be placed against the entire surface of the shoring prior to pouring the foundation wall. Weep pipes located no more than 6 feet on-center should be connected to the drainage composite and poured into the foundation walls or the perimeter footing. A footing drain installed along the inside of the perimeter footing will be used to collect and carry the water discharged by the weep pipes to the storm system. Isolated zones of moisture or seepage can still reach the permanent wall where groundwater finds leaks or joints in the drainage composite. This is often an acceptable risk in unoccupied below-grade spaces, such as parking garages. However, formal waterproofing is typically necessary in areas where wet conditions at the face of the permanent wall will not be tolerable. If this is a concern, the permanent drainage and waterproofing system should be designed by a specialty consultant familiar with the expected subsurface conditions and proposed construction. Plate 6 presents typical considerations for foundation drains at shoring walls. These drains should be surrounded by at least 6 inches of 1-inch-minus, washed rock that is encircled with non-woven, geotextile filter fabric (Mirafi 140N, Supac 4NP, or similar material). At its highest point, a perforated pipe invert should be at least 6 inches below the bottom of a slab floor or the level of a crawl space. The discharge pipe for subsurface drains should be sloped for flow to the outlet point. Roof and surface water drains must not discharge into the foundation drain system. A typical footing drain detail is attached to this report as Plate 7. Underdrainage should be used where: (1) crawl spaces or basements will be below a structure; (2) a slab is below the outside grade; or (3) the outside grade does not slope downward from a building. Drains should also be placed at the base of all earth-retaining walls. As noted in the General section, we recommend underdrainage for a basement floor slab, in the event that unexpected rises in the groundwater levels occur. An underslab drainage detail is attached to this report as Plate 8. For the best long-term performance, perforated PVC pipe is recommended for all subsurface drains. Clean-outs should be provided for potential future flushing or cleaning of footing drains. If the structure includes an elevator with an elevator pit, it will be necessary to provide watertight construction for the elevator pit. As a minimum, a vapor retarder, as defined in the Slabs-On-Grade section, should be provided in any crawl space area to limit the transmission of water vapor from the underlying soils. Crawl space grades are sometimes left near the elevation of the bottom of the footings. As a result, an outlet drain is recommended for all crawl spaces to prevent an accumulation of any water that may bypass the footing drains. Providing a few inches of free draining gravel underneath the vapor retarder is also prudent to limit the potential for seepage to build up on top of the vapor retarder. Groundwater was observed during our field work. If seepage is encountered in an excavation, it should be drained from the site by directing it through drainage ditches, perforated pipe, or French DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 Williams Avenue Ventures LLC JN 22149 May 24, 2022 Page 16 GEOTECH CONSULTANTS, INC. drains, or by pumping it from sumps interconnected by shallow connector trenches at the bottom of the excavation. The excavation and site should be graded so that surface water is directed off the site and away from the tops of slopes. Water should not be allowed to stand in any area where foundations, slabs, or pavements are to be constructed. Final site grading in areas adjacent to the building should slope away at least one to 2 percent, except where the area is paved. Surface drains should be provided where necessary to prevent ponding of water behind foundation or retaining walls. A discussion of grading and drainage related to pervious surfaces near walls and structures is contained in the Foundation and Retaining Walls section. GENERAL EARTHWORK AND STRUCTURAL FILL All building and pavement areas should be stripped of surface vegetation, topsoil, organic soil, and other deleterious material. It is important that existing foundations be removed before site development. The stripped or removed materials should not be mixed with any materials to be used as structural fill, but they could be used in non-structural areas, such as landscape beds. Structural fill is defined as any fill, including utility backfill, placed under, or close to, a building, or in other areas where the underlying soil needs to support loads. All structural fill should be placed in horizontal lifts with a moisture content at, or near, the optimum moisture content. The optimum moisture content is that moisture content that results in the greatest compacted dry density. The moisture content of fill is very important and must be closely controlled during the filling and compaction process. The allowable thickness of the fill lift will depend on the material type selected, the compaction equipment used, and the number of passes made to compact the lift. The loose lift thickness should not exceed 12 inches, but should be thinner if small, hand-operated compactors are used. We recommend testing structural fill as it is placed. If the fill is not sufficiently compacted, it should be recompacted before another lift is placed. This eliminates the need to remove the fill to achieve the required compaction. The following table presents recommended levels of relative compaction for compacted fill: LOCATION OF FILL PLACEMENT MINIMUM RELATIVE COMPACTION Beneath slabs or walkways 95% Filled slopes and behind retaining walls 90% Beneath pavements 95% for upper 12 inches of subgrade; 90% below that level Where: Minimum Relative Compaction is the ratio, expressed in percentages, of the compacted dry density to the maximum dry density, as determined in accordance with ASTM Test Designation D 1557-91 (Modified Proctor). DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 Williams Avenue Ventures LLC JN 22149 May 24, 2022 Page 17 GEOTECH CONSULTANTS, INC. LIMITATIONS The conclusions and recommendations contained in this report are based on site conditions as they existed at the time of our exploration and assume that the soil and groundwater conditions encountered in the explorations are representative of subsurface conditions on the site. If the subsurface conditions encountered during construction are significantly different from those observed in our explorations, we should be advised at once so that we can review these conditions and reconsider our recommendations where necessary. Unanticipated conditions are commonly encountered on construction sites and cannot be fully anticipated by the limited area of subsurface explorations, especially while the properties are still developed and occupied. Subsurface conditions can also vary between exploration locations. Such unexpected conditions frequently require making additional expenditures to attain a properly constructed project. It is recommended that the owner consider providing a contingency fund to accommodate such potential extra costs and risks. This is a standard recommendation for all projects. This report has been prepared for the exclusive use of Williams Avenue Ventures LLC and its representatives, for specific application to this project and site. Our conclusions and recommendations are professional opinions derived in accordance with our understanding of current local standards of practice, and within the scope of our services. No warranty is expressed or implied. The scope of our services does not include services related to construction safety precautions, and our recommendations are not intended to direct the contractor's methods, techniques, sequences, or procedures, except as specifically described in our report for consideration in design. Our services also do not include assessing or minimizing the potential for biological hazards, such as mold, bacteria, mildew and fungi in either the existing or proposed site development. ADDITIONAL SERVICES In addition to reviewing the final plans, Geotech Consultants, Inc. should be retained to provide geotechnical consultation, testing, and observation services during construction. This is to confirm that subsurface conditions are consistent with those indicated by our exploration, to evaluate whether earthwork and foundation construction activities comply with the general intent of the recommendations presented in this report, and to provide suggestions for design changes in the event subsurface conditions differ from those anticipated prior to the start of construction. However, our work would not include the supervision or direction of the actual work of the contractor and its employees or agents. Also, job and site safety, and dimensional measurements, will be the responsibility of the contractor. During the construction phase, we will provide geotechnical observation and testing services when requested by you or your representatives. Please be aware that we can only document site work we actually observe. It is still the responsibility of your contractor or on-site construction team to verify that our recommendations are being followed, whether we are present at the site or not. DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 Williams Avenue Ventures LLC JN 22149 May 24, 2022 Page 18 GEOTECH CONSULTANTS, INC. The following plates are attached to complete this report: Plate 1 Vicinity Map Plate 2 Site Exploration Plan Plates 3 - 5 Cone Penetration Test Logs Plate 6 Typical Shoring Drain Detail Plate 7 Typical Footing Drain Detail Plate 8 Typical Underslab Drainage Detail We appreciate the opportunity to be of service on this project. Please contact us if you have any questions, or if we can be of further assistance. Respectfully submitted, GEOTECH CONSULTANTS, INC. 5/24/2022 Marc R. McGinnis, P.E. Principal MKM/MRM:kg DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 Job No:Date:Plate: 22149 May 2022 GEOTECH CONSULTANTS, INC. 99-107 Williams Avenue South Renton, Washington VICINITY MAP (Source: King County iMap) 1 SITE DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 Job No:Date:Plate: 22149 May 2022 GEOTECH CONSULTANTS, INC. 99-107 Williams Avenue South Renton, Washington SITE EXPLORATION PLAN 2 No Scale Legend: Cone Penetration Test Location CPT-1 CPT-3 CPT-2 DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 Job Date:Plate: 22149 GEOTECH CONSULTANTS, INC. CONE PENETRATION TEST LOG May 2022 Logged by: 99-107 Williams Avenue South Renton, Washington 3 DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 Job Date:Plate: 22149 GEOTECH CONSULTANTS, INC. CONE PENETRATION TEST LOG May 2022 Logged by: 99-107 Williams Avenue South Renton, Washington 4 DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 Job Date:Plate: 22149 GEOTECH CONSULTANTS, INC. CONE PENETRATION TEST LOG May 2022 Logged by: 99-107 Williams Avenue South Renton, Washington 5 DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 Job No:Date:Plate: 22149 May 2022 GEOTECH CONSULTANTS, INC. 99-107 Williams Avenue South Renton, Washington 6 SHORING DRAIN DETAIL Foundation wall & Footing Treated lagging Soldier pile Drainage composite Vapor retarder Slab 4" perforated PVC drain (holes turned downward) 2" PVC weep pipe at 6' centers (Pour into footing or wall below slab) Non-woven filter fabric Washed rock or pea gravel Attach weep pipe to drainage composite. Pierce waterproofing and plastic backing of drainage composite. Note - Refer to the report for additional considerations related to drainage and waterproofing. Waterproofing DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 Job No:Date:Plate: 22149 May 2022 GEOTECH CONSULTANTS, INC. 99-107 Williams Avenue South Renton, Washington 7 FOOTING DRAIN DETAIL Washed Rock (7/8" min. size) Slope backfill away from foundation. Provide surface drains where necessary. 4" min. 4" Perforated Hard PVC Pipe (Invert at least 6 inches below slab or crawl space. Slope to drain to appropriate outfall. Place holes downward.) Tightline Roof Drain (Do not connect to footing drain) Nonwoven Geotextile Filter Fabric NOTES: (1) In crawl spaces, provide an outlet drain to prevent buildup of water that bypasses the perimeter footing drains. (2) Refer to report text for additional drainage, waterproofing, and slab considerations. Backfill (See text for requirements) Vapor Retarder/Barrier and Capillary Break/Drainage Layer (Refer to Report text) Possible Slab DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 Job No:Date:Plate: 22149 May 2022 GEOTECH CONSULTANTS, INC. 99-107 Williams Avenue South Renton, Washington NOTES: (1) Refer to the report text for additional drainage and waterproofing considerations. (2) The typical maximum underslab drain separation (L) is 15 to 20 feet. (3) No filter fabric is necessary beneath the pipes as long as a minimum thickness of 4 inches of rock is maintained beneath the pipes. (4) The underslab drains and foundation drains should discharge to a suitable outfall. 4-inch perforated PVC pipe (slope to drain) Pea gravel or drain rock L L L 9 to 12 inches Vapor Retarder or Waterproof Vapor Barrier TYPICAL UNDERSLAB DRAINAGE 8 DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 2023 D. R. STRONG Consulting Engineers Inc. Page 43 Camellia Court Technical Information Report Renton, Washington SECTION VII OTHER PERMITS, VARIANCES AND ADJUSTMENTS None at this time. DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 2023 D. R. STRONG Consulting Engineers Inc. Page 44 Camellia Court Technical Information Report Renton, Washington SECTION VIII CSWPPP ANALYSIS AND DESIGN (PART A) The Erosion and Sedimentation Control Design will meet the seven minimum King County requirements: 1. Areas to remain undisturbed shall be delineated with a high visibility plastic fence prior to any site clearing or grading. 2. Site disturbed areas shall be covered with mulch and seeded, as appropriate, for temporary or permanent measures. 3. Perimeter protection shall consist of a silt fence down slope of any disturbed areas or stockpiles. 4. A stabilized construction entrance will be located at the point of ingress/egress (i.e. onsite access road). 5. The detention pond will act as a sediment pond for sediment retention. Perimeter silt fences will provide sediment retention within the bypass areas. 6. Surface water from disturbed areas will sheet flow to the sediment pond for treatment. 7. Dust control shall be provided by spraying exposed soils with water until wet. This is required when exposed soils are dry to the point that wind transport is possible which would impact roadways, drainage ways, surface waters, or neighboring residences. SWPPP PLAN DESIGN (PART B) Construction activities that could contribute pollutants to surface and storm water include the following, with applicable BMP’s listed for each item: 1. Storage and use of chemicals: Utilize source control, and soil erosion and sedimentation control practices, such as using only recommended amounts of chemical materials applied in the proper manner; neutralizing concrete wash water, and disposing of excess concrete material only in areas prepared for concrete placement, or return to batch plant; disposing of wash-up waters from water-based paints in sanitary sewer; disposing of wastes from oil-based paints, solvents, thinners, and mineral spirits only through a licensed waste management firm, or treatment, storage, and disposal (TSD) facility. 2. Material delivery and storage: Locate temporary storage areas away from vehicular traffic, near the construction entrance, and away from storm drains. Material Safety Data Sheets (MSDS) should be supplied for all materials stored, and chemicals kept in their original labeled containers. Maintenance, fueling, and repair of heavy equipment and vehicles shall be conducted using spill prevention and control measures. Contaminated surfaces shall be cleaned immediately following any spill incident. Provide cover, containment, and protection from vandalism for all chemicals, liquid products, petroleum products, and other potentially hazardous materials. DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 2023 D. R. STRONG Consulting Engineers Inc. Page 45 Camellia Court Technical Information Report Renton, Washington 3. Building demolition: Protect stormwater drainage system from sediment-laden runoff and loose particles. To the extent possible, use dikes, berms, or other methods to protect overland discharge paths from runoff. Street gutter, sidewalks, driveways, and other paved surfaces in the immediate area of demolition must be swept daily to collect and properly dispose of loose debris and garbage. Spray the minimum amount of water to help control windblown fine particles such as concrete, dust, and paint chips. Avoid excessive spraying so that runoff from the site does not occur, yet dust control is achieved. Oils must never be used for dust control. 4. Sawcutting: Slurry and cuttings shall be vacuumed during the activity to prevent migration offsite and must not remain on permanent concrete or asphalt paving overnight. Collected slurry and cuttings shall be disposed of in a manner that does not violate ground water or surface water quality standards. A formal CSWPPP will be submitted with final engineering. DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 2023 D. R. STRONG Consulting Engineers Inc. Page 46 Camellia Court Technical Information Report Renton, Washington SECTION IX BOND QUANTITIES, FACILITY SUMMARIES, AND DECLARATION OF COVENANT 1. Bond Quantity Worksheet – To be provided at time of final engineering DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 2023 D. R. STRONG Consulting Engineers Inc. Page 47 Camellia Court Technical Information Report Renton, Washington SECTION X OPERATIONS AND MAINTENANCE MANUAL To be provided at time of final engineering. DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 2023 D. R. STRONG Consulting Engineers Inc. Page 48 Camellia Court Technical Information Report Renton, Washington APPENDICES DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 2023 D. R. STRONG Consulting Engineers Inc. Page 49 Camellia Court Technical Information Report Renton, Washington APPENDIX “A” LEGAL DESCRIPTION PARCEL NO. 0007200096 (99 WILLIAMS AVE S) BEGINNING AT THE NORTHEAST CORNER OF BLOCK 24 IN THE TOWN OF RENTON, AS RECORDED IN VOLUME 1 OF PLATS, ON PAGE 135, RECORDS OF KING COUNTY, WASHINGTON; THENCE WEST ALONG THE NORTH LINE OF SAID BLOCK 115 FEET; THENCE NORTH AND PARALLEL TO THE CENTER LINE OF WILLIAMS ST. 50 FEET; THENCE EAST AND PARALLEL TO THE NORTH LINE OF SAID BLOCK, 115 FEET; THENCE SOUTH ALONG THE EAST LINE OF WILLIAMS ST. 50 FEET TO THE POINT OF BEGINNING. SITUATE IN THE COUNTY OF KING, STATE OF WASHINGTON PARCEL NO. 7231502130 (101 WILLIAMS AVE S) LOT 20, BLOCK 24, TOWN OF RENTON, ACCORDING TO THE PLAT THEREOF RECORDED IN VOLUME 1 OF PLATS, PAGE 135, IN KING COUNTY, WASHINGTON; EXCEPT THE WEST 5 FEET THEREOF HERETOFORE CONVEYED TO THE CITY OF RENTON FOR ALLEY, BY DEED RECORDED UNDER AUDITOR'S FILE NO. 2117471. SITUATE IN THE COUNTY OF KING, STATE OF WASHINGTON PARCEL NO. 7231502125 (107 WILLIAMS AVE S) LOT 19, BLOCK 24, TOWN OF RENTON, ACCORDING TO THE PLAT THEREOF RECORDED IN VOLUME 1 OF PLATS, PAGE 135, IN KING COUNTY, WASHINGTON; EXCEPT THE WEST 5 FEET THEREOF, CONVEYED TO THE CITY OF RENTON FOR ALLEY PURPOSES, BY DEED RECORDED UNDER AUDITOR'S FILE NO. 2117484. SITUATE IN THE COUNTY OF KING, STATE OF WASHINGTON DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 2023 D. R. STRONG Consulting Engineers Inc. Page 50 Camellia Court Technical Information Report Renton, Washington APPENDIX “B” WWHM MODELING RESULTS DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 WWHM2012 PROJECT REPORT DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 23003 8/2/2023 8:26:42 AM Page 2 General Model Information WWHM2012 Project Name:23003 Site Name:Camellia Apartments Site Address:99 Williams Ave S City:Renton Report Date:8/2/2023 Gage:Seatac Data Start:1948/10/01 Data End:2009/09/30 Timestep:15 Minute Precip Scale:1.000 Version Date:2023/01/27 Version:4.2.19 POC Thresholds Low Flow Threshold for POC1:50 Percent of the 2 Year High Flow Threshold for POC1:50 Year DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 23003 8/2/2023 8:26:42 AM Page 3 Landuse Basin Data Predeveloped Land Use Basin 1 Bypass:No GroundWater:No Pervious Land Use acre A B, Lawn, Flat 0.183 Pervious Total 0.183 Impervious Land Use acre ROADS FLAT 0.034 ROOF TOPS FLAT 0.185 SIDEWALKS FLAT 0.036 Impervious Total 0.255 Basin Total 0.438 DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 23003 8/2/2023 8:26:42 AM Page 4 Mitigated Land Use Basin 1 Bypass:No GroundWater:No Pervious Land Use acre A B, Lawn, Flat 0.003 Pervious Total 0.003 Impervious Land Use acre ROADS FLAT 0.019 ROOF TOPS FLAT 0.373 SIDEWALKS FLAT 0.043 Impervious Total 0.435 Basin Total 0.438 DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 23003 8/2/2023 8:26:42 AM Page 5 Routing Elements Predeveloped Routing DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 23003 8/2/2023 8:26:42 AM Page 6 Mitigated Routing DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 23003 8/2/2023 8:26:42 AM Page 7 Analysis Results POC 1 + Predeveloped x Mitigated Predeveloped Landuse Totals for POC #1 Total Pervious Area:0.183 Total Impervious Area:0.255 Mitigated Landuse Totals for POC #1 Total Pervious Area:0.003 Total Impervious Area:0.435 Flow Frequency Method:Log Pearson Type III 17B Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year 0.098145 5 year 0.125825 10 year 0.145241 25 year 0.171067 50 year 0.191277 100 year 0.212347 Flow Frequency Return Periods for Mitigated. POC #1 Return Period Flow(cfs) 2 year 0.165869 5 year 0.209525 10 year 0.239187 25 year 0.277666 50 year 0.307117 100 year 0.337284 Annual Peaks Annual Peaks for Predeveloped and Mitigated. POC #1 Year Predeveloped Mitigated 1949 0.127 0.215 1950 0.136 0.232 1951 0.084 0.134 1952 0.070 0.119 1953 0.076 0.129 1954 0.081 0.135 1955 0.090 0.153 1956 0.088 0.150 1957 0.100 0.171 1958 0.081 0.138 DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 23003 8/2/2023 8:27:09 AM Page 8 1959 0.082 0.140 1960 0.081 0.138 1961 0.086 0.146 1962 0.074 0.127 1963 0.084 0.141 1964 0.081 0.138 1965 0.104 0.176 1966 0.069 0.118 1967 0.119 0.203 1968 0.135 0.230 1969 0.094 0.160 1970 0.091 0.154 1971 0.108 0.184 1972 0.123 0.190 1973 0.068 0.115 1974 0.099 0.168 1975 0.114 0.194 1976 0.077 0.130 1977 0.083 0.141 1978 0.101 0.173 1979 0.138 0.236 1980 0.124 0.212 1981 0.102 0.173 1982 0.143 0.244 1983 0.117 0.199 1984 0.074 0.125 1985 0.101 0.173 1986 0.088 0.150 1987 0.136 0.231 1988 0.082 0.140 1989 0.103 0.175 1990 0.210 0.296 1991 0.148 0.236 1992 0.073 0.124 1993 0.063 0.108 1994 0.069 0.117 1995 0.090 0.154 1996 0.105 0.164 1997 0.097 0.159 1998 0.094 0.161 1999 0.193 0.329 2000 0.096 0.164 2001 0.106 0.180 2002 0.123 0.210 2003 0.097 0.163 2004 0.181 0.308 2005 0.083 0.141 2006 0.077 0.124 2007 0.197 0.288 2008 0.142 0.232 2009 0.126 0.214 Ranked Annual Peaks Ranked Annual Peaks for Predeveloped and Mitigated. POC #1 Rank Predeveloped Mitigated 1 0.2101 0.3293 2 0.1972 0.3081 3 0.1931 0.2962 DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 23003 8/2/2023 8:27:09 AM Page 9 4 0.1807 0.2880 5 0.1481 0.2444 6 0.1433 0.2363 7 0.1418 0.2362 8 0.1384 0.2321 9 0.1361 0.2321 10 0.1356 0.2312 11 0.1351 0.2304 12 0.1268 0.2148 13 0.1257 0.2144 14 0.1242 0.2119 15 0.1232 0.2101 16 0.1231 0.2026 17 0.1188 0.1989 18 0.1166 0.1937 19 0.1135 0.1904 20 0.1080 0.1843 21 0.1056 0.1801 22 0.1052 0.1759 23 0.1045 0.1754 24 0.1029 0.1733 25 0.1016 0.1729 26 0.1014 0.1725 27 0.1011 0.1707 28 0.1001 0.1681 29 0.0986 0.1639 30 0.0975 0.1636 31 0.0968 0.1633 32 0.0964 0.1610 33 0.0944 0.1601 34 0.0939 0.1589 35 0.0906 0.1545 36 0.0901 0.1537 37 0.0897 0.1529 38 0.0882 0.1505 39 0.0879 0.1499 40 0.0855 0.1458 41 0.0841 0.1412 42 0.0838 0.1410 43 0.0827 0.1408 44 0.0827 0.1405 45 0.0824 0.1403 46 0.0824 0.1384 47 0.0811 0.1379 48 0.0811 0.1377 49 0.0811 0.1349 50 0.0807 0.1343 51 0.0770 0.1302 52 0.0767 0.1289 53 0.0756 0.1271 54 0.0745 0.1255 55 0.0737 0.1245 56 0.0728 0.1243 57 0.0701 0.1194 58 0.0691 0.1176 59 0.0688 0.1171 60 0.0675 0.1152 61 0.0631 0.1076 DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 23003 8/2/2023 8:27:09 AM Page 10 DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 23003 8/2/2023 8:27:09 AM Page 11 Duration Flows The Duration Matching Failed Flow(cfs)Predev Mit Percentage Pass/Fail 0.0491 1760 8801 500 Fail 0.0505 1593 8215 515 Fail 0.0519 1432 7567 528 Fail 0.0534 1296 7026 542 Fail 0.0548 1170 6528 557 Fail 0.0563 1055 6074 575 Fail 0.0577 963 5683 590 Fail 0.0591 885 5285 597 Fail 0.0606 810 4924 607 Fail 0.0620 736 4581 622 Fail 0.0634 677 4284 632 Fail 0.0649 614 3991 650 Fail 0.0663 571 3737 654 Fail 0.0677 531 3493 657 Fail 0.0692 486 3298 678 Fail 0.0706 454 3110 685 Fail 0.0721 423 2913 688 Fail 0.0735 390 2719 697 Fail 0.0749 366 2560 699 Fail 0.0764 339 2408 710 Fail 0.0778 316 2267 717 Fail 0.0792 290 2127 733 Fail 0.0807 268 1998 745 Fail 0.0821 247 1872 757 Fail 0.0835 231 1756 760 Fail 0.0850 216 1657 767 Fail 0.0864 201 1550 771 Fail 0.0879 188 1446 769 Fail 0.0893 176 1367 776 Fail 0.0907 160 1290 806 Fail 0.0922 150 1215 810 Fail 0.0936 145 1138 784 Fail 0.0950 135 1060 785 Fail 0.0965 127 1003 789 Fail 0.0979 118 954 808 Fail 0.0993 113 898 794 Fail 0.1008 110 864 785 Fail 0.1022 96 823 857 Fail 0.1037 94 777 826 Fail 0.1051 86 741 861 Fail 0.1065 79 706 893 Fail 0.1080 75 664 885 Fail 0.1094 73 623 853 Fail 0.1108 71 601 846 Fail 0.1123 69 573 830 Fail 0.1137 62 549 885 Fail 0.1151 61 521 854 Fail 0.1166 59 498 844 Fail 0.1180 57 466 817 Fail 0.1195 52 445 855 Fail 0.1209 48 424 883 Fail 0.1223 43 408 948 Fail 0.1238 37 389 1051 Fail 0.1252 35 370 1057 Fail DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 23003 8/2/2023 8:27:09 AM Page 12 0.1266 32 355 1109 Fail 0.1281 30 340 1133 Fail 0.1295 28 323 1153 Fail 0.1309 26 311 1196 Fail 0.1324 25 299 1196 Fail 0.1338 24 282 1175 Fail 0.1353 22 270 1227 Fail 0.1367 19 261 1373 Fail 0.1381 18 249 1383 Fail 0.1396 17 238 1400 Fail 0.1410 15 228 1520 Fail 0.1424 14 218 1557 Fail 0.1439 13 209 1607 Fail 0.1453 13 199 1530 Fail 0.1467 12 187 1558 Fail 0.1482 11 181 1645 Fail 0.1496 10 178 1779 Fail 0.1511 10 171 1710 Fail 0.1525 10 166 1660 Fail 0.1539 10 153 1530 Fail 0.1554 10 148 1480 Fail 0.1568 9 142 1577 Fail 0.1582 9 139 1544 Fail 0.1597 9 135 1500 Fail 0.1611 8 127 1587 Fail 0.1625 8 121 1512 Fail 0.1640 8 116 1450 Fail 0.1654 7 110 1571 Fail 0.1669 7 107 1528 Fail 0.1683 7 106 1514 Fail 0.1697 6 104 1733 Fail 0.1712 6 100 1666 Fail 0.1726 5 95 1900 Fail 0.1740 5 90 1800 Fail 0.1755 5 89 1779 Fail 0.1769 4 84 2100 Fail 0.1783 4 83 2075 Fail 0.1798 4 76 1900 Fail 0.1812 3 72 2400 Fail 0.1827 3 71 2366 Fail 0.1841 3 68 2266 Fail 0.1855 3 65 2166 Fail 0.1870 3 64 2133 Fail 0.1884 3 63 2100 Fail 0.1898 3 62 2066 Fail 0.1913 3 59 1966 Fail The development has an increase in flow durations from 1/2 Predeveloped 2 year flow to the 2 year flow or more than a 10% increase from the 2 year to the 50 year flow. The development has an increase in flow durations for more than 50% of the flows for the range of the duration analysis. DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 23003 8/2/2023 8:27:09 AM Page 13 Water Quality Water Quality BMP Flow and Volume for POC #1 On-line facility volume:0 acre-feet On-line facility target flow:0 cfs. Adjusted for 15 min:0 cfs. Off-line facility target flow:0 cfs. Adjusted for 15 min:0 cfs. DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 23003 8/2/2023 8:27:09 AM Page 14 LID Report DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 23003 8/2/2023 8:27:27 AM Page 15 Model Default Modifications Total of 0 changes have been made. PERLND Changes No PERLND changes have been made. IMPLND Changes No IMPLND changes have been made. DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 23003 8/2/2023 8:27:27 AM Page 16 Appendix Predeveloped Schematic DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 23003 8/2/2023 8:27:29 AM Page 17 Mitigated Schematic DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 23003 8/2/2023 8:27:30 AM Page 18 Predeveloped UCI File RUN GLOBAL WWHM4 model simulation START 1948 10 01 END 2009 09 30 RUN INTERP OUTPUT LEVEL 3 0 RESUME 0 RUN 1 UNIT SYSTEM 1 END GLOBAL FILES <File> <Un#> <-----------File Name------------------------------>*** <-ID-> *** WDM 26 23003.wdm MESSU 25 Pre23003.MES 27 Pre23003.L61 28 Pre23003.L62 30 POC230031.dat END FILES OPN SEQUENCE INGRP INDELT 00:15 PERLND 7 IMPLND 1 IMPLND 4 IMPLND 8 COPY 501 DISPLY 1 END INGRP END OPN SEQUENCE DISPLY DISPLY-INFO1 # - #<----------Title----------->***TRAN PIVL DIG1 FIL1 PYR DIG2 FIL2 YRND 1 Basin 1 MAX 1 2 30 9 END DISPLY-INFO1 END DISPLY COPY TIMESERIES # - # NPT NMN *** 1 1 1 501 1 1 END TIMESERIES END COPY GENER OPCODE # # OPCD *** END OPCODE PARM # # K *** END PARM END GENER PERLND GEN-INFO <PLS ><-------Name------->NBLKS Unit-systems Printer *** # - # User t-series Engl Metr *** in out *** 7 A/B, Lawn, Flat 1 1 1 1 27 0 END GEN-INFO *** Section PWATER*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC *** 7 0 0 1 0 0 0 0 0 0 0 0 0 END ACTIVITY PRINT-INFO <PLS > ***************** Print-flags ***************************** PIVL PYR # - # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC ********* DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 23003 8/2/2023 8:27:30 AM Page 19 7 0 0 4 0 0 0 0 0 0 0 0 0 1 9 END PRINT-INFO PWAT-PARM1 <PLS > PWATER variable monthly parameter value flags *** # - # CSNO RTOP UZFG VCS VUZ VNN VIFW VIRC VLE INFC HWT *** 7 0 0 0 0 0 0 0 0 0 0 0 END PWAT-PARM1 PWAT-PARM2 <PLS > PWATER input info: Part 2 *** # - # ***FOREST LZSN INFILT LSUR SLSUR KVARY AGWRC 7 0 5 0.8 400 0.05 0.3 0.996 END PWAT-PARM2 PWAT-PARM3 <PLS > PWATER input info: Part 3 *** # - # ***PETMAX PETMIN INFEXP INFILD DEEPFR BASETP AGWETP 7 0 0 2 2 0 0 0 END PWAT-PARM3 PWAT-PARM4 <PLS > PWATER input info: Part 4 *** # - # CEPSC UZSN NSUR INTFW IRC LZETP *** 7 0.1 0.5 0.25 0 0.7 0.25 END PWAT-PARM4 PWAT-STATE1 <PLS > *** Initial conditions at start of simulation ran from 1990 to end of 1992 (pat 1-11-95) RUN 21 *** # - # *** CEPS SURS UZS IFWS LZS AGWS GWVS 7 0 0 0 0 3 1 0 END PWAT-STATE1 END PERLND IMPLND GEN-INFO <PLS ><-------Name-------> Unit-systems Printer *** # - # User t-series Engl Metr *** in out *** 1 ROADS/FLAT 1 1 1 27 0 4 ROOF TOPS/FLAT 1 1 1 27 0 8 SIDEWALKS/FLAT 1 1 1 27 0 END GEN-INFO *** Section IWATER*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # ATMP SNOW IWAT SLD IWG IQAL *** 1 0 0 1 0 0 0 4 0 0 1 0 0 0 8 0 0 1 0 0 0 END ACTIVITY PRINT-INFO <ILS > ******** Print-flags ******** PIVL PYR # - # ATMP SNOW IWAT SLD IWG IQAL ********* 1 0 0 4 0 0 0 1 9 4 0 0 4 0 0 0 1 9 8 0 0 4 0 0 0 1 9 END PRINT-INFO IWAT-PARM1 <PLS > IWATER variable monthly parameter value flags *** # - # CSNO RTOP VRS VNN RTLI *** 1 0 0 0 0 0 4 0 0 0 0 0 8 0 0 0 0 0 END IWAT-PARM1 DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 23003 8/2/2023 8:27:30 AM Page 20 IWAT-PARM2 <PLS > IWATER input info: Part 2 *** # - # *** LSUR SLSUR NSUR RETSC 1 400 0.01 0.1 0.1 4 400 0.01 0.1 0.1 8 400 0.01 0.1 0.1 END IWAT-PARM2 IWAT-PARM3 <PLS > IWATER input info: Part 3 *** # - # ***PETMAX PETMIN 1 0 0 4 0 0 8 0 0 END IWAT-PARM3 IWAT-STATE1 <PLS > *** Initial conditions at start of simulation # - # *** RETS SURS 1 0 0 4 0 0 8 0 0 END IWAT-STATE1 END IMPLND SCHEMATIC <-Source-> <--Area--> <-Target-> MBLK *** <Name> # <-factor-> <Name> # Tbl# *** Basin 1*** PERLND 7 0.183 COPY 501 12 PERLND 7 0.183 COPY 501 13 IMPLND 1 0.034 COPY 501 15 IMPLND 4 0.185 COPY 501 15 IMPLND 8 0.036 COPY 501 15 ******Routing****** END SCHEMATIC NETWORK <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # #<-factor->strg <Name> # # <Name> # # *** COPY 501 OUTPUT MEAN 1 1 48.4 DISPLY 1 INPUT TIMSER 1 <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # #<-factor->strg <Name> # # <Name> # # *** END NETWORK RCHRES GEN-INFO RCHRES Name Nexits Unit Systems Printer *** # - #<------------------><---> User T-series Engl Metr LKFG *** in out *** END GEN-INFO *** Section RCHRES*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # HYFG ADFG CNFG HTFG SDFG GQFG OXFG NUFG PKFG PHFG *** END ACTIVITY PRINT-INFO <PLS > ***************** Print-flags ******************* PIVL PYR # - # HYDR ADCA CONS HEAT SED GQL OXRX NUTR PLNK PHCB PIVL PYR ********* END PRINT-INFO HYDR-PARM1 RCHRES Flags for each HYDR Section *** DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 23003 8/2/2023 8:27:30 AM Page 21 # - # VC A1 A2 A3 ODFVFG for each *** ODGTFG for each FUNCT for each FG FG FG FG possible exit *** possible exit possible exit * * * * * * * * * * * * * * *** END HYDR-PARM1 HYDR-PARM2 # - # FTABNO LEN DELTH STCOR KS DB50 *** <------><--------><--------><--------><--------><--------><--------> *** END HYDR-PARM2 HYDR-INIT RCHRES Initial conditions for each HYDR section *** # - # *** VOL Initial value of COLIND Initial value of OUTDGT *** ac-ft for each possible exit for each possible exit <------><--------> <---><---><---><---><---> *** <---><---><---><---><---> END HYDR-INIT END RCHRES SPEC-ACTIONS END SPEC-ACTIONS FTABLES END FTABLES EXT SOURCES <-Volume-> <Member> SsysSgap<--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # tem strg<-factor->strg <Name> # # <Name> # # *** WDM 2 PREC ENGL 1 PERLND 1 999 EXTNL PREC WDM 2 PREC ENGL 1 IMPLND 1 999 EXTNL PREC WDM 1 EVAP ENGL 0.76 PERLND 1 999 EXTNL PETINP WDM 1 EVAP ENGL 0.76 IMPLND 1 999 EXTNL PETINP END EXT SOURCES EXT TARGETS <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Volume-> <Member> Tsys Tgap Amd *** <Name> # <Name> # #<-factor->strg <Name> # <Name> tem strg strg*** COPY 501 OUTPUT MEAN 1 1 48.4 WDM 501 FLOW ENGL REPL END EXT TARGETS MASS-LINK <Volume> <-Grp> <-Member-><--Mult--> <Target> <-Grp> <-Member->*** <Name> <Name> # #<-factor-> <Name> <Name> # #*** MASS-LINK 12 PERLND PWATER SURO 0.083333 COPY INPUT MEAN END MASS-LINK 12 MASS-LINK 13 PERLND PWATER IFWO 0.083333 COPY INPUT MEAN END MASS-LINK 13 MASS-LINK 15 IMPLND IWATER SURO 0.083333 COPY INPUT MEAN END MASS-LINK 15 END MASS-LINK END RUN DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 23003 8/2/2023 8:27:30 AM Page 22 Mitigated UCI File RUN GLOBAL WWHM4 model simulation START 1948 10 01 END 2009 09 30 RUN INTERP OUTPUT LEVEL 3 0 RESUME 0 RUN 1 UNIT SYSTEM 1 END GLOBAL FILES <File> <Un#> <-----------File Name------------------------------>*** <-ID-> *** WDM 26 23003.wdm MESSU 25 Mit23003.MES 27 Mit23003.L61 28 Mit23003.L62 30 POC230031.dat END FILES OPN SEQUENCE INGRP INDELT 00:15 PERLND 7 IMPLND 1 IMPLND 4 IMPLND 8 COPY 501 DISPLY 1 END INGRP END OPN SEQUENCE DISPLY DISPLY-INFO1 # - #<----------Title----------->***TRAN PIVL DIG1 FIL1 PYR DIG2 FIL2 YRND 1 Basin 1 MAX 1 2 30 9 END DISPLY-INFO1 END DISPLY COPY TIMESERIES # - # NPT NMN *** 1 1 1 501 1 1 END TIMESERIES END COPY GENER OPCODE # # OPCD *** END OPCODE PARM # # K *** END PARM END GENER PERLND GEN-INFO <PLS ><-------Name------->NBLKS Unit-systems Printer *** # - # User t-series Engl Metr *** in out *** 7 A/B, Lawn, Flat 1 1 1 1 27 0 END GEN-INFO *** Section PWATER*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC *** 7 0 0 1 0 0 0 0 0 0 0 0 0 END ACTIVITY PRINT-INFO <PLS > ***************** Print-flags ***************************** PIVL PYR # - # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC ********* DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 23003 8/2/2023 8:27:30 AM Page 23 7 0 0 4 0 0 0 0 0 0 0 0 0 1 9 END PRINT-INFO PWAT-PARM1 <PLS > PWATER variable monthly parameter value flags *** # - # CSNO RTOP UZFG VCS VUZ VNN VIFW VIRC VLE INFC HWT *** 7 0 0 0 0 0 0 0 0 0 0 0 END PWAT-PARM1 PWAT-PARM2 <PLS > PWATER input info: Part 2 *** # - # ***FOREST LZSN INFILT LSUR SLSUR KVARY AGWRC 7 0 5 0.8 400 0.05 0.3 0.996 END PWAT-PARM2 PWAT-PARM3 <PLS > PWATER input info: Part 3 *** # - # ***PETMAX PETMIN INFEXP INFILD DEEPFR BASETP AGWETP 7 0 0 2 2 0 0 0 END PWAT-PARM3 PWAT-PARM4 <PLS > PWATER input info: Part 4 *** # - # CEPSC UZSN NSUR INTFW IRC LZETP *** 7 0.1 0.5 0.25 0 0.7 0.25 END PWAT-PARM4 PWAT-STATE1 <PLS > *** Initial conditions at start of simulation ran from 1990 to end of 1992 (pat 1-11-95) RUN 21 *** # - # *** CEPS SURS UZS IFWS LZS AGWS GWVS 7 0 0 0 0 3 1 0 END PWAT-STATE1 END PERLND IMPLND GEN-INFO <PLS ><-------Name-------> Unit-systems Printer *** # - # User t-series Engl Metr *** in out *** 1 ROADS/FLAT 1 1 1 27 0 4 ROOF TOPS/FLAT 1 1 1 27 0 8 SIDEWALKS/FLAT 1 1 1 27 0 END GEN-INFO *** Section IWATER*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # ATMP SNOW IWAT SLD IWG IQAL *** 1 0 0 1 0 0 0 4 0 0 1 0 0 0 8 0 0 1 0 0 0 END ACTIVITY PRINT-INFO <ILS > ******** Print-flags ******** PIVL PYR # - # ATMP SNOW IWAT SLD IWG IQAL ********* 1 0 0 4 0 0 4 1 9 4 0 0 4 0 0 0 1 9 8 0 0 4 0 0 0 1 9 END PRINT-INFO IWAT-PARM1 <PLS > IWATER variable monthly parameter value flags *** # - # CSNO RTOP VRS VNN RTLI *** 1 0 0 0 0 0 4 0 0 0 0 0 8 0 0 0 0 0 END IWAT-PARM1 DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 23003 8/2/2023 8:27:30 AM Page 24 IWAT-PARM2 <PLS > IWATER input info: Part 2 *** # - # *** LSUR SLSUR NSUR RETSC 1 400 0.01 0.1 0.1 4 400 0.01 0.1 0.1 8 400 0.01 0.1 0.1 END IWAT-PARM2 IWAT-PARM3 <PLS > IWATER input info: Part 3 *** # - # ***PETMAX PETMIN 1 0 0 4 0 0 8 0 0 END IWAT-PARM3 IWAT-STATE1 <PLS > *** Initial conditions at start of simulation # - # *** RETS SURS 1 0 0 4 0 0 8 0 0 END IWAT-STATE1 END IMPLND SCHEMATIC <-Source-> <--Area--> <-Target-> MBLK *** <Name> # <-factor-> <Name> # Tbl# *** Basin 1*** PERLND 7 0.003 COPY 501 12 PERLND 7 0.003 COPY 501 13 IMPLND 1 0.019 COPY 501 15 IMPLND 4 0.373 COPY 501 15 IMPLND 8 0.043 COPY 501 15 ******Routing****** END SCHEMATIC NETWORK <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # #<-factor->strg <Name> # # <Name> # # *** COPY 501 OUTPUT MEAN 1 1 48.4 DISPLY 1 INPUT TIMSER 1 <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # #<-factor->strg <Name> # # <Name> # # *** END NETWORK RCHRES GEN-INFO RCHRES Name Nexits Unit Systems Printer *** # - #<------------------><---> User T-series Engl Metr LKFG *** in out *** END GEN-INFO *** Section RCHRES*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # HYFG ADFG CNFG HTFG SDFG GQFG OXFG NUFG PKFG PHFG *** END ACTIVITY PRINT-INFO <PLS > ***************** Print-flags ******************* PIVL PYR # - # HYDR ADCA CONS HEAT SED GQL OXRX NUTR PLNK PHCB PIVL PYR ********* END PRINT-INFO HYDR-PARM1 RCHRES Flags for each HYDR Section *** DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 23003 8/2/2023 8:27:30 AM Page 25 # - # VC A1 A2 A3 ODFVFG for each *** ODGTFG for each FUNCT for each FG FG FG FG possible exit *** possible exit possible exit * * * * * * * * * * * * * * *** END HYDR-PARM1 HYDR-PARM2 # - # FTABNO LEN DELTH STCOR KS DB50 *** <------><--------><--------><--------><--------><--------><--------> *** END HYDR-PARM2 HYDR-INIT RCHRES Initial conditions for each HYDR section *** # - # *** VOL Initial value of COLIND Initial value of OUTDGT *** ac-ft for each possible exit for each possible exit <------><--------> <---><---><---><---><---> *** <---><---><---><---><---> END HYDR-INIT END RCHRES SPEC-ACTIONS END SPEC-ACTIONS FTABLES END FTABLES EXT SOURCES <-Volume-> <Member> SsysSgap<--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # tem strg<-factor->strg <Name> # # <Name> # # *** WDM 2 PREC ENGL 1 PERLND 1 999 EXTNL PREC WDM 2 PREC ENGL 1 IMPLND 1 999 EXTNL PREC WDM 1 EVAP ENGL 0.76 PERLND 1 999 EXTNL PETINP WDM 1 EVAP ENGL 0.76 IMPLND 1 999 EXTNL PETINP END EXT SOURCES EXT TARGETS <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Volume-> <Member> Tsys Tgap Amd *** <Name> # <Name> # #<-factor->strg <Name> # <Name> tem strg strg*** COPY 1 OUTPUT MEAN 1 1 48.4 WDM 701 FLOW ENGL REPL COPY 501 OUTPUT MEAN 1 1 48.4 WDM 801 FLOW ENGL REPL END EXT TARGETS MASS-LINK <Volume> <-Grp> <-Member-><--Mult--> <Target> <-Grp> <-Member->*** <Name> <Name> # #<-factor-> <Name> <Name> # #*** MASS-LINK 12 PERLND PWATER SURO 0.083333 COPY INPUT MEAN END MASS-LINK 12 MASS-LINK 13 PERLND PWATER IFWO 0.083333 COPY INPUT MEAN END MASS-LINK 13 MASS-LINK 15 IMPLND IWATER SURO 0.083333 COPY INPUT MEAN END MASS-LINK 15 END MASS-LINK END RUN DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 23003 8/2/2023 8:27:30 AM Page 26 Predeveloped HSPF Message File DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 23003 8/2/2023 8:27:30 AM Page 27 Mitigated HSPF Message File DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 23003 8/2/2023 8:27:30 AM Page 28 Disclaimer Legal Notice This program and accompanying documentation are provided 'as-is' without warranty of any kind. The entire risk regarding the performance and results of this program is assumed by End User. Clear Creek Solutions Inc. and the governmental licensee or sublicensees disclaim all warranties, either expressed or implied, including but not limited to implied warranties of program and accompanying documentation. In no event shall Clear Creek Solutions Inc. be liable for any damages whatsoever (including without limitation to damages for loss of business profits, loss of business information, business interruption, and the like) arising out of the use of, or inability to use this program even if Clear Creek Solutions Inc. or their authorized representatives have been advised of the possibility of such damages. Software Copyright © by : Clear Creek Solutions, Inc. 2005-2023; All Rights Reserved. Clear Creek Solutions, Inc. 6200 Capitol Blvd. Ste F Olympia, WA. 98501 Toll Free 1(866)943-0304 Local (360)943-0304 www.clearcreeksolutions.com DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1 2023 D. R. STRONG Consulting Engineers Inc. Page 51 Camellia Court Technical Information Report Renton, Washington APPENDIX “C” BOND QUANTITY WORKSHEET DocuSign Envelope ID: E380154C-A526-42C6-9A09-974E2B481BE1